PDF Optimizer options

You can reduce the size of a PDF by selecting options from the panels in the PDF Optimizer dialog box.

Images panel

The Images panel of the PDF Optimizer lets you set options for color, grayscale, and monochrome image compression.

In the Images panel, you can select the following options:

Downsample Reduces file size by lowering the resolution of images, which involves merging the colors of original pixels into larger pixels.

Note: Masked images and images of less than 16-by-16 pixels are not downsampled.

Compression Reduces file size by eliminating unnecessary pixel data. In general, JPEG and JPEG2000 compression give better results on images like photographs with gradual transitions from color to color. ZIP is the better choice for illustrations with large areas of solid, flat color or patterns made up of flat colors. For monochrome images, JBIG2 compression, which is available in PDF Optimizer but not in Acrobat Distiller, is superior to CCITT.

Quality Can be set only for JPEG and JPEG2000 compression. JPEG and JPEG2000 compression methods are typically lossy, a process that permanently removes some pixel data. You can apply lossy JPEG or JPEG2000 compression to color images at various levels (minimum, low, medium, high, maximum). For JPEG2000 compression, you can also specify lossless so that no pixel data is removed. Compression for monochrome images is lossless, except for JBIG2 compression, which provides both lossy and lossless modes of compression.

Fonts panel

To ensure an exact match to the source document, you should embed all fonts used in the document. If an exact match is not needed and you prefer a smaller file, you can choose not to embed fonts for roman text and East Asian text (Traditional Chinese, Simplified Chinese, Korean, and Japanese). Text in these languages is replaced with a substitution font when viewed on a system that does not have the original fonts. The Fonts panel of the PDF Optimizer contains two lists for fonts, fonts that are available for unembedding, and fonts to be unembedded. Certain fonts aren’t available for unembedding and don’t appear in the Fonts panel. To unembed fonts in a document, select one or more fonts in the Embedded Fonts list, and click the Unembed button. If you change your mind about unembedding a font, select it in the list on the right and click the Retain button.

Transparency panel

If your PDF includes artwork that contains transparency, you can use presets in the Transparency panel of PDF Optimizer to flatten transparency and reduce file size. (Flattening incorporates transparency into corresponding artwork by sectioning it into vector-based areas and rasterized areas.) PDF Optimizer applies transparency options to all pages in the document before applying other optimization options.

If you select the Acrobat 4.0 And Later compatibility setting, the Transparency panel is enabled and all transparency in the file is flattened during optimization. This ensures compatibility with Acrobat 5.0 and earlier, which doesn’t support transparency.

When you create flattening presets, they appear with the default presets in the Transparency panel.

Note: Transparency flattening cannot be undone after the file is saved.

Discard Objects panel

The Discard Objects panel lets you specify objects to remove from the PDF and lets you optimize curved lines in CAD drawings. You can discard objects created in Acrobat and in other applications. Selecting an object removes all occurrences of that object within the PDF.

In the Discard Objects area, you can select from these and other options:

Discard All Form Submission, Import And Reset Actions Disables all actions related to submitting or importing form data, and resets form fields. This option retains form objects to which actions are linked.

Flatten Form Fields Makes form fields unusable with no change to their appearance. Form data is merged with the page to become page content.

Discard All JavaScript Actions Removes any actions in the PDF that use JavaScript.

Discard All Alternate Images Removes all versions of an image except the one destined for on-screen viewing. Some PDFs include multiple versions of the same image for different purposes, such as low-resolution on-screen viewing and high-resolution printing.

Discard Embedded Page Thumbnails Removes embedded page thumbnails. This is useful for large documents, which can take a long time to draw page thumbnails after you click the Pages button.

Discard Document Tags Removes tags from the document, which also removes the accessibility and reflow capabilities for the text.

Convert Smooth Lines To Curves Reduces the number of control points used to build curves in CAD drawings, which results in smaller PDF files and faster on-screen rendering.

Detect And Merge Image Fragments Looks for images or masks that are fragmented into thin slices and tries to merge the slices into a single image or mask.

Discard Embedded Print Settings Removes embedded print settings, such as page scaling and duplex mode, from the document.

Discard Embedded Search Index Removes embedded search indexes, which reduces file size.

Discard Bookmarks Removes all bookmarks from the document.

Discard User Data panel

Use the Discard User Data panel to remove any personal information that you don’t want to distribute or share with others. If you’re unable to find personal information, it may be hidden. You can locate hidden text and user-related information by using Examine Document command from the Document menu.

Discard Document Information And Metadata Removes information in the document information dictionary and all metadata streams. (Use the Save As command to restore metadata streams to a copy of the PDF.)

Discard All Object Data Removes all objects from the PDF.

Discard File Attachments Removes all file attachments, including attachments added to the PDF as comments. (PDF Optimizer doesn’t optimize attached files.)

Discard External Cross References Removes links to other documents. Links that jump to other locations within the PDF are not removed.

Discard Private Data Of Other Applications Strips information from a PDF document that is useful only to the application that created the document. This does not affect the functionality of the PDF, but it does decrease the file size.

Discard Hidden Layer Content And Flatten Visible Layers Decreases file size. The optimized document looks like the original PDF but doesn’t contain layer information.

Clean Up panel

The options in the Clean Up panel of the PDF Optimizer remove useless items from the document. These items include elements that are obsolete or unnecessary to your intended use of the document. Be aware that removing certain elements may seriously affect the functionality of the PDF. By default, only elements that do not affect functionality are selected. If you are unsure of the implications of removing other options, you should use the default selections.

In the Clean Up area, you can select these options:

Use Flate To Encode Streams That Are Not Encoded Applies Flate compression to all streams that aren’t encoded.

In Streams That Use LZW Encoding, Use Flate Instead Applies Flate compression all content streams and images that use LZW encoding.

Remove Invalid Bookmarks Removes bookmarks that point to pages in the document that have been deleted.

Remove Invalid Links Removes links that jump to invalid destinations.

Remove Unreferenced Named Destinations Removes named destinations that are not being referenced internally from within the PDF document. Because this option does not check for links from other PDF files or websites, it may not fit in some workflows.

Optimize The PDF For Fast Web View Restructures a PDF document for page-at-a-time downloading (byte-serving) from web servers.

Source: Adobe