Font handling in Acrobat Distiller when creating PDF files
- About Windows and Mac OS fonts
- How Acrobat Distiller uses fonts
- How font types affect text in PDF files
- How PostScript printer drivers handle TrueType fonts in Windows
The fonts you use determine your output when you convert documents to PDF format in Adobe Acrobat Distiller. (Acrobat Distiller is both a feature of Adobe Acrobat and a stand-alone application.) The font type (such as TrueType, PostScript) affects the general appearance of text in the PDF file and whether that text can be searched, edited, or printed.
Use this document to understand how Acrobat Distiller handle fonts and improve your PDF output.
About Windows and Mac OS fonts
Acrobat Distiller recognizes all Windows and Mac OS fonts; however, the type of font that you use (for example, TrueType) determines how Acrobat Distiller handles the information for that font.
Windows font types include: Type 1 fonts (or PostScript fonts), Type 3 fonts, Windows bitmap and vector fonts, TrueType fonts, and Open Type Fonts from Adobe (Windows 2000 and XP). Mac OS font types include: Type 1 fonts, Apple TrueType dFonts, TrueType fonts, and OpenType Fonts from Adobe.
In addition to the font type, Acrobat Distiller uses the font character set to determine what font information to include in the PDF files it creates. Character sets for Type 1 fonts, for example, can include one or more of the ISO Latin 1, Expert, Small Capitals and Old Style Figures (SC & OSF), Symbolic, Cyrillic, and Kanji character sets:
-- The ISO Latin 1 character set (or standard Type 1 character set) includes the standard English, French, Italian, and German alphabet characters, as well as punctuation characters and numbers.
-- Expert character sets include fraction and ligature characters for the English alphabet.
-- SC & OSF character sets contain specially designed letters and numbers to customize a document's appearance.
-- Symbol character sets contain non-text characters, rather than alphabet characters.
-- Cyrillic character sets contain the alphabet characters for languages, such as Russian and Ukrainian.
-- Kanji (Japanese) character sets contain double-byte Japanese characters. See the Kanji Fonts section of this document for information about when you can use and view Kanji fonts in PDF files.
How Acrobat Distiller uses fonts
For Acrobat Distiller to successfully convert a document to a PDF document, it must reference each font in the original document through the following processes as the document is converted first to PostScript, then to PDF.
Checking for the PostScript name
Acrobat Distiller looks for a PostScript font name and adds it to the PDF document. PostScript font names are usually listed in the name table of a font. (The name table stores font information, such as name, style, and copyright.) If a PostScript name isn't available, Acrobat Distiller uses the system's name for the font. For example, if the original document includes a TrueType font that's installed on the system, Acrobat Distiller derives the BaseFont and FontName from the font's name table.
If the font is a Type 42 font, Acrobat Distiller creates a name table for the font from a matching system font; Type42 fonts typically don't include name tables. For more information about Type 42 fonts, see "TrueType Fonts" in the "How Font Types Affect Text in PDF Files" section of this document.
Adding a description of the fonts
To each PDF file it creates, Acrobat Distiller adds a description of Type 1 fonts that use the ISO Latin 1 character set. If you open a PDF file on a computer that has these fonts installed, Acrobat uses the installed fonts to display and print the PDF file. If the fonts aren't installed, Acrobat uses the font descriptions to create substitute fonts that resemble the original fonts.
Embedding the fonts
If font embedding is enabled, Acrobat Distiller embeds TrueType and Type 3 fonts, and Type 1 fonts that don't use the ISO Latin 1 character set (such as symbol or expert characters). Acrobat Distiller 7.0 can embed OpenType fonts; however, the application that created the original document determines which OpenType font characteristics can be embedded. If you embed an OpenType font that is based on a Type 1 font, Acrobat Distiller embeds it as a CFF/Type 2 font. Acrobat Distiller embeds Open Type fonts that are based on TrueType fonts as TrueType fonts.
A font that is embedded in a PDF file is always available for viewing and printing, whether or not it's installed on the system. However, you cannot edit text in the PDF file unless the font is installed. If you try to edit text that uses an embedded font and the font isn't installed, Acrobat returns a warning and uses a substitute font instead.
Acrobat Distiller acknowledges and preserves the original font permissions, even if a PDF file is redistilled. Fonts that have restricted permissions can't be embedded and will cause Acrobat Distiller to return an error during the conversion process. Similarly, fonts that don't use a character encoding format, such as WinAnsi or MacRoman, may cause Acrobat Distiller to return an error if you try to embed them.
Converting the fonts
If Acrobat Distiller can't interpret or find the font information it needs from a font, it substitutes the font. In rare instances, Acrobat Distiller converts such fonts to bitmap images, which prevents the font from being searched, scaled, or edited. Acrobat Distiller typically converts PCL fonts and Windows vector (outline) fonts to bitmap images. See the "How Postscript Printer Drivers Handle TrueType Fontsin Windows" section in this document.
Acrobat Distiller embeds a font descriptor (that is, font information) for each font that it embeds. A descriptor can include the following information:
|Descriptor||What the descriptor means|
|Ascent||The maximum height above the baseline reached by the characters in the font, excluding accents.|
|CapHeight||The y-coordinate of the top of the flat capital letters (for example, 'E'), measured from the baseline.|
|Descent||The maximum depth below the baseline reached by characters in the font.|
|Flags||The attributes of the font, including fixed-width, serif, symbolic, script, italic, small caps, all caps, or other attributes.|
|FontBBox||A bounding box that is the smallest rectangle capable of containing any characters in the character set if drawn on top of each other.|
|ItalicAngle||The angle in degrees of the dominant vertical strokes; usually negative.|
|StemV||The width of the vertical stems in characters.|
|AvgWidth (optional)||The average width of characters in the font.|
|FontFile (optional)||The complete typeface outline. Present only when the font or font subset is embedded.|
|Leading (optional)||The desired line spacing between lines of text.|
|MaxWidth (optional)||The maximum width of characters in the font.|
|MissingWidth (optional)||The width to use with unencoded characters (that is, those not included in the character set).|
|StemH (optional)||The width of horizontal stems in characters.|
|XHeight (optional)||The y-coordinate of the top of the flat non-ascending lowercase characters (for example, "z"), measured from the baseline.|
|FontFamily (optional)||The family to which the font belongs (for example, typeface "Times Bold Italic" belongs to the "Times" FontFamily).|
|FontStretch (optional)||A variation of the font that affects the horizontal dimension (for example, UltraCondensed, SemiCondensed, Normal, Expanded).|
|FontWeight (optional)||The weight or thickness of a font.|
How font types affect text in PDF files
The type of font you use can affect how text in your PDF files appears and prints, and whether or not the text is searchable and editable
If a PDF file contains fonts that have been converted to bitmap images, the viewers won't process the images as fonts, but will instead display and print the images just like any other bitmap images. Text converted to bitmaps, however, isn't searchable or editable.
dFonts (Mac OSX only)
These fonts are native to the Mac OS X system and are identical to standard font suitcase files except that the font resources are stored in the data fork of the file. Acrobat Distiller handles dFonts the same as other TrueType fonts on Mac OS.
You can create PDF files that contain Kanji fonts using both Kanji and English-language versions of Acrobat Distiller. (For English-language versions of Acrobat Distiller, you must install the appropriate font support package.) Acrobat automatically displays Asian fonts that are embedded in a PDF file. If Asian fonts aren't embedded, Acrobat can display them after you install the appropriate font support package. For information about installing font support packages, see document , "Viewing and Printing Asian Fonts in PDF Files Using Roman Acrobat Viewers."
Multiple Master (MM) fonts
Because multiple master fonts (such as Minion MM) create specific instances of a font based on the properties of a document and where the font is used, Acrobat Distiller cannot embed them. Instead, Acrobat Distiller adds a subset of the font, which has a unique font ID. Because MM fonts generate these instances dynamically, you cannot embed the fonts or edit them in Acrobat. Adobe Technical Support recommends that you don't use MM fonts if you need to edit or embed fonts in Acrobat. For more information on MM fonts, see document 328600 , "Multiple Master Fonts General Information."
OpenType Fonts from Adobe
OpenType format is based on Type 1 and combine outline, metric, and bitmap data into a single font file. OpenType format includes advanced typography features that most applications have not yet taken advantage of; as a result, these applications recognize and treat OpenType format as TrueType fonts. This treatment affects the way OpenType Fonts from Adobe are embedded in PDF files. Type 1 font embedding requirements apply to Type 1-based Open Type Fonts from Adobe. TrueType embedding requirements apply to TrueType-based OpenType fonts.
You can embed OpenType Fonts from Adobe in Acrobat Distiller 7.0 if you select PDF 1.6 compatibility, however the OpenType-specific features will be available only in Acrobat 7.0. (Choose Settings > Edit Adobe PDF Settings, click the General tab and choose Acrobat 7.0 (PDF 1.6) from the Compatibility pop-up menu.)
Because each symbol font contains unique characters and character sets, Acrobat Distiller always embed these fonts to prevent them from being substituted.
TrueType fonts that have installation and editing permissions can be embedded in a PDF file by Acrobat Distiller. If the font doesn't include these permissions, Acrobat Distiller embeds a font subset (that is, only the characters of the font that are used in the document).
Note:Acrobat Distiller doesn't report subsets of TrueType fonts in its log file. And even though the TouchUp Text tool in Acrobat lists the fonts as embedded in the Text Attributes dialog box, you cannot edit a font subset with this tool because the system can't recognize the font subset's unique font ID and map it to the original TrueType font on the system. If you edit a font subset with the TouchUp Text Tool, Acrobat substitutes the font with a sans serif or serif equivalent.
When you use Acrobat Distiller to create PDF files, text formatted with TrueType fonts may not be searchable, depending on how the font information was written into the PostScript file. In these cases, PostScript printers convert the TrueType font as a Type 42 font, which best preserves the font's characteristics, such as searchability. The Type 42 font format exists primarily as a way for PostScript interpreters to download non-PostScript (TrueType) fonts. A Type 42 font consists of a PostScript language "wrapper" around a TrueType font. A Type 42 font is usually generated by a printer driver to download TrueType fonts to a PostScript printer that includes a TrueType rasterizer. By this method the TrueType font is interpreted directly by Acrobat Distiller, which provides the most accurate description of the original TrueType font. Variables that can affect this font information include: the application that created the PostScript file, the font itself, the PostScript printer driver, and the PostScript Printer Description (PPD) file. If text formatted with TrueType fonts is unsearchable in a PDF file created with Acrobat Distiller, change one or more of these variables and then re-create the PDF file.
Information is written into a PostScript file either by the application that generates PostScript code or by the PostScript printer driver. For more information, see that application's documentation, or see "How Postscript Printer Drivers Handle TrueType Fonts in Windows" in this document.
Type 1 fonts
For both appearance and searchability, Type 1 fonts offer reliable conversion to PDF. Because Type 1 fonts don't need to be converted to another format when the font (or a subset of the font) is embedded in a PostScript file, they offer the best results when you use Acrobat Distiller.
To embed Type 1 fonts, the following conditions must be met:
1. In the Adobe PDF Settings dialog box, the font appears in the AlwaysEmbed list in the Fonts tab and EmbedAllFonts is set to True.
2. No symbols are used (except the symbol for pi).
3. The font size is within an appropriate range (this is, the CharStrings dict leng value is greater than 115 but less than 229). You can check the CharStrings dict leng value in a font editing application.
Type 3 fonts
Because Type 3 fonts use the entire PostScript computer language to express a font, they can include specifications that Type 1 fonts cannot, such as shading, color, and fill. However, Type 3 fonts aren't optimized for size or performance, so characters may appear bolder than their Type 1 counterparts.
Type 3 fonts are always embedded in PDF files, so they're always available in Acrobat or Adobe Reader (except on Mac OS X, which doesn't support Type 3 fonts). Acrobat and Adobe Reader convert the Type 3 characters to bitmap images and then display them. When you print to a PostScript printer, Acrobat and Adobe Reader use your PostScript printer driver to download the font to the printer. When you print to a non-PostScript printer, the bitmap images print. Type 3 font characters in the ISO Latin 1 character set convert to searchable text in PDF files, although those in the symbol character sets do not. PDF files with embedded Type 3 fonts usually have larger file sizes than those with embedded Type 1 fonts.
How Postscript printer drivers handle TrueType fonts in Windows
When TrueType fonts are sent through the Adobe PostScript printer driver as encoded Type 42 (called Native TrueType in Windows 2000 and XP) or character identifier (CID) fonts (in the case of double-byte or Unicode fonts), the printer driver gives font characters specific font IDs rather than standard font ID information, causing Acrobat Distiller to embed a subset of the font in the PostScript file.
By including a subset of a font, the printer driver decreases the file size, which in turn increases the speed of PostScript file conversion. This process occurs regardless of whether the job options are set to Embed All Fonts.
To embed the entire font when printing to the Adobe PDF printer, you must enable Do Not Send Fonts To Adobe PDF in the Font tab of the Adobe PDF Printer Settings dialog box.
The Adobe PostScript printer driver (AdobePS) for Windows 98, and NT 4.0 includes Send Fonts As settings that control how TrueType fonts are sent to a printer or included in a PostScript file. The Pscript5 printer driver (pscript5.dll) and later for Windows 2000 and later includes TrueType Download settings that control how TrueType fonts are sent to a printer or included in a PostScript file. You can change the settings in the driver's Properties dialog box (Windows 98, and NT 4.0) or in the driver's Advanced Options dialog box (Windows 2000 and XP). The settings vary depending on the features specified in the printer's PPD file. The Microsoft PostScript printer driver for Windows 98 and NT 4.0 includes fewer Send Fonts As settings than AdobePS. For example, the Microsoft PostScript printer driver doesn't include options to send TrueType fonts as Type 42 or Outline fonts.
Use the following guidelines when selecting Send Fonts As settings:
Send Fonts As (Windows 98, or NT 4.0) or TrueType Font Download Option (Windows 2000 and XP)
Outline (AdobePS for Windows 98 or NT, pscript5.dll for Windows 2000 or XP)
With this option, the printer driver uses a font's outline metrics for display and print. This option gives text the look and feel of a font, but text doesn't retain actual font information. This option is often used when a font cannot be embedded due to licensing restrictions. Outline fonts aren't searchable or editable.
As Bitmaps (AdobePS and Windows PostScript printer driver, pscript5.dll for Windows 2000 or XP)
With this option, the printer driver converts TrueType fonts to Type 3 bitmaps. If you don't or can't use the Type 42 (native) option, this option provides greater accuracy in simulating the original TrueType font. Unlike actual Type 3 fonts, however, Type 3 bitmaps aren't searchable. Use this option for text that's formatted at 14 points or smaller, or when printing to low resolution printers. Don't use this option for portable files (for example, EPS files), since it can increase file size.
Native TrueType (AdobePS and Windows PostScript printer driver)
When you distill a document that contains a TrueType font, Acrobat Distiller doesn't recognize the font coding language (because it isn't PostScript), and substitutes a Type 1 PostScript font. Sending TrueType fonts as Type 42 fonts preserves their appearance and prevents substitution with Type 1 fonts.This option is best for preserving text searchability. Keep in mind, however, that other variables also affect searchability.
Don't Send (AdobePS and Windows PostScript printer driver)
With this option, the printer driver won't include TrueType font information in the PostScript file. This option is recommended only for printers or network spoolers that supply fonts.
Bitmap/Outline threshold setting (AdobePS and Windows PostScript printer driver)
This option specifies how small a font's point size must be before it is sent as a bitmap rather than as an outline. Setting the threshold to 1 will prevent fonts from being sent as bitmaps.
Softfont or Device Font (AdobePS for Windows NT and Windows PostScript printer driver for Windows NT)
With the Softfont option, the printer driver sends font description information. This option helps retain appearance, but not searchability. With the Device Font option, the printer driver lets you customize a font substitution table to match each installed font with a printer-resident font. This option may not retain a font's exact appearance, but does retain searchability.
Viewing and Printing Asian Fonts in PDF Files Using Roman Acrobat Viewers
328600 : Multiple Master Fonts General Information.