Understanding Adobe PDF

About Adobe PDF

Portable Document Format (PDF) is a universal file format that preserves the fonts, images, and layout of source documents created on a wide range of applications and platforms. Adobe PDF is the standard for the secure, reliable distribution and exchange of electronic documents and forms around the world. Adobe PDF files are compact and complete, and can be shared, viewed, and printed by anyone with free Adobe Reader® software.

Adobe PDF is highly effective in print publishing workflows. By saving a composite of your artwork in Adobe PDF, you create a compact, reliable file that you or your service provider can view, edit, organize, and proof. Then, at the appropriate time in the workflow, your service provider can either output the Adobe PDF file directly, or process it using tools from various sources for such post-processing tasks as preflight checks, trapping, imposition, and color separation.

When you save in Adobe PDF, you can choose to create a PDF/X-compliant file. PDF/X (Portable Document Format Exchange) is a subset of Adobe PDF that eliminates many of the color, font, and trapping variables that lead to printing problems. PDF/X may be used wherever PDFs are exchanged as digital masters for print production—whether at the creation or output stage of the workflow, as long as the applications and output devices support PDF/X.

Adobe PDFs can solve the following problems associated with electronic documents:

Common problem

Adobe PDF solution

Recipients can't open files because they don't have the applications used to create the files.

Anyone, anywhere can open a PDF. All you need is the free Adobe Reader software.

Combined paper and electronic archives are difficult to search, take up space, and require the application in which a document was created.

PDFs are compact and fully searchable, and can be accessed at any time using Reader. Links make PDFs easy to navigate.

Documents appear incorrectly on handheld devices.

Tagged PDFs allow text to reflow for display on mobile platforms such as Palm OS®, Symbian™, and Pocket PC® devices.

Documents with complex formatting are not accessible to visually impaired readers.

Tagged PDFs contain information on content and structure, which makes them accessible on-screen readers.

Embedding and substituting fonts

InCopy embeds a font only if it contains a setting by the font vendor that permits it to be embedded. Embedding prevents font substitution when a reader views or prints the file, and ensures that readers see the text in its original font. Embedding increases the file size only slightly, unless the document uses CID (multibyte) fonts, a font format commonly used for Asian languages, where multiple characters are combined to create a single glyph.

For each font embedded, InCopy can embed the entire font or just a subset—the particular characters, called glyphs, used in the file. Subsetting ensures that your fonts and font metrics are used at print time by creating a custom font name. The subsetting options you choose affect disk space and your ability to do late-stage editing.

If InCopy cannot embed a font, it temporarily substitutes the font with a Multiple Master typeface: either AdobeSerMM for a missing serif font, or AdobeSanMM for a missing sans serif font.

These typefaces can stretch or condense to fit, to ensure that line and page breaks are maintained from the original document. The substitution cannot always match the shape of the original characters, however, especially if the characters are unconventional ones, such as script typefaces.

If characters are unconventional (left), the substitution font cannot always match (right).

About compression

When exporting to Adobe PDF, InCopy automatically downsamples images, crops image data to the image’s frame, and compresses text and line art using the lossless ZIP method. ZIP works well on images with large areas of single colors or repeating patterns, and for black-and-white images that contain repeating patterns. Because InCopy uses the lossless ZIP method, data is not removed to reduce file size, so image quality is not affected.

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