Method
Last updated on
Oct 25, 2026
Learn about the compression, downsampling, font embedding, and transparency settings available when you export PDF files from Adobe Illustrator.
Refer to these settings when balancing PDF file size and image quality for web delivery, print production, or archival storage. The Compression and Advanced sections of the Save Adobe PDF dialog box control how Illustrator processes bitmap images, text, line art, and fonts during PDF creation.
Select a downsampling method
Downsampling reduces the number of pixels in an image. Select a method based on your output requirements and the quality trade-offs you can accept.
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Description |
Best for |
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Average Downsampling To |
Averages the pixels in a sample area and replaces the area with the average color at the specified resolution |
General-purpose use with balanced quality and file size |
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Bicubic Downsampling To |
Uses a weighted average to determine pixel color, preserving smoother tonal transitions |
High-quality output where smooth gradations matter |
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Subsampling To |
Selects a single pixel from the center of the sample area and replaces the entire area with that pixel color |
Fastest conversion when speed matters more than smoothness |
Illustrator downsamples images above the threshold resolution specified in For Images Above. Disabling downsampling preserves the original image resolution.
Select a compression type
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Compression type |
Characteristics |
Suitable for |
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Automatic (JPEG) |
Uses JPEG compression with automatic quality detection |
Maximum compatibility across PDF readers |
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Automatic (JPEG2000) |
Applies the JPEG2000 standard for superior compression |
Workflows that need progressive display and smaller file sizes |
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ZIP |
Lossless or lossy, depending on the Quality setting |
Images with large single-color areas, repeating patterns, or repeating black-and-white patterns |
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JPEG |
Lossy compression that removes image data to reduce file size |
Grayscale or color photographs where some quality loss is acceptable |
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JPEG2000 |
International standard supporting progressive display and ICC color management |
Grayscale or color images that need both compression efficiency and advanced features |
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Consultative Committee on International Telegraphy and Telephony (CCITT) Group 3 |
Compresses monochrome bitmaps one row at a time |
Fax-quality monochrome images |
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CCITT Group 4 |
General-purpose method for monochrome images |
Black-and-white images and 1-bit scanned artwork |
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Run Length |
Produces the best results for images with large solid areas |
Monochrome images with extensive black or white regions |
Note
CCITT and Run Length compression are available only for monochrome bitmap images.
Review image quality settings
Image quality determines the amount of compression applied. The available options depend on the compression method you select.
JPEG compression quality levels
Minimum: Highest compression, lowest quality
Low: Significant compression with noticeable quality reduction
Medium: Balanced compression and quality
High: Minimal compression with very good quality
Maximum: Least compression, best quality
ZIP compression quality levels
4-bit compression is lossless for 4-bit images, but may reduce 8-bit images to 4-bit. 8-bit compression is lossless for 4-bit and 8-bit images.
Additional compression controls
Tile Size (JPEG2000 only): This option is enabled only when Compression is set to JPEG2000 or Automatic (JPEG2000).
Compress Text and Line Art: This compression method preserves detail and quality without data loss.
Font embedding options
The Subset fonts when percent of characters used is less than the setting, which controls when Illustrator embeds only the characters used in a document. For example, if a font contains 1,000 characters but your document uses only 10 of them, embedding the complete font adds unnecessary file size.
A higher percentage causes Illustrator to subset more fonts, embedding only the characters used. A lower percentage embeds more complete fonts. If you need editing flexibility or font consistency across multiple documents, lower the threshold to 0% to always embed complete fonts.
Review overprint and transparency settings
Overprints: Controls how overlapping colors set to overprint are saved in the PDF.
Preserve: Maintains overprint settings for reproduction on printing presses.
Discard: Removes overprint attributes.
Simulate: Flattens artwork to simulate overprinting (available only when Compatibility is set to Acrobat 4 / PDF 1.3).
Preset: When Compatibility is set to Acrobat 4 (PDF 1.3) and the artwork contains transparency, the Preset option offers transparency-flattening choices, including Custom. Acrobat 5 (PDF 1.4) and later versions automatically preserve live transparency, so this option is unavailable at those compatibility levels.
For detailed guidance on transparency flattening presets and their effects on printing, learn how to print and save transparent artwork.
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