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Optimizing your PDF Documents with Acrobat 9

Learn how to clean up your PDF documents using optimization methods available in Acrobat 9.

By July 31, 2009


Cleaning up your PDF documents

There is much more to a PDF document than the obvious text and images. Other entities range from comments and attachments to layers and information from the document’s source program that you may not want or need to save. Acrobat 9 Professional offers several mechanisms for examining, optimizing and dealing with PDF document content.

Acrobat 9 offers four methods for optimizing files (Figure 1). Each method listed increases in complexity and time involved to complete the task from left to right on the continuum. However, the amount of control and customization increases from left to right as well.

Figure 1: Choose a file optimization method according to your needs.

Your choices include the following:

  • The simplest method uses the File > Save As command. Acrobat discards auto-saved iterations of the document and cleans up the file to decrease the file size.
  • Let Acrobat optimize the file with a single command using the Reduce File Size command. Choose Document > Reduce File Size to open the dialog box. Choose an Acrobat version compatibility from the dropdown list—the newer the version, the greater potential reduction in file size.
  • To select general types of extraneous material—such as comments and hidden text—turn to the Examine Document command.
  • For making a document the most efficient file size without sacrificing quality, use the PDF Optimizer.

Examining a PDF file

The Examine Document feature is essentially a subset of the PDF Optimizer and contains the most prevalent and commonly removed file elements.

Open the file you want to evaluate and follow these steps:

1. Choose Document > Examine Document. Acrobat processes the active document and opens the Examine Document panel, listing items found and options to show details (Figure 2).

Figure 2: Select existing content to remove from the file.

Tip: An Alert dialog box displays if there are attached PDF files explaining that the process applies only to the current file, and that you have to open the attachments and run the process separately for examining the attachments.

2. Check through the features identified. Table 1 lists the types of content examined, such as reviewing hidden text, or text overlaid by other text or in white on various pages of the file (Figure 3).

Figure 3: Review hidden and visible text in the preview dialog box.

3. Clear checkmarks for any features you want to preserve and click Remove to display the Examine Document information dialog box. As noted in the dialog box, other program items are automatically removed when you delete content, including digital signatures, Reader-enabled rights, review and forms workflows and information added by third-party applications. Click OK to close the information dialog box and process the file.

4. The Examine Document panel lists the changes made. Save the file to preserve the modifications.
Tip: Once saved, you can’t revert to the unprocessed document state. Save the file with another name if you may need the original content in the future.

Table 1: Types of information that can be removed

Content type

Type of content

Where to view in Acrobat


Information about the document used for searching and managing files, such as content, keywords, subject and author’s name

Choose File > Properties

File attachments

Files attached to the file before generating the PDF file from the source program, or those attached within Acrobat

Choose View > Navigation Panels > Attachments

Annotations and comments

All comments added to the document using the Comments & Markup tools, any files attached as comments

Choose View > Navigation Panels > Comments

Form field logic or actions

Form fields—including signature fields—are flattened, actions and calculations are removed

Choose Forms > Add or Edit Fields or View > Navigation Panels > Signatures

Hidden text

Text in the PDF document that is covered by an image or other text, is transparent, or uses the same color as the background

Click Show Preview on the Examine PDF panel

Hidden layers

The layers in a document can be specified as hidden or shown; hidden layers are deleted and remaining layers are flattened into a single layer

Choose View > Navigation Panels > Layers


A panel listing of text items used for linking to specific locations and magnifications in the document

Choose View > Navigation Panels > Bookmarks

Embedded search index

A text index embedded into a file to speed up search processes

Choose Advanced > Document Processing > Manage Embedded Index

Hidden page and image content

Content removed from a document such as text or images or cropped page segments are included as file elements

Optimizing PDF documents


Change a program preference to examine files automatically if your workflow includes routine examining for sensitive and hidden content before e-mailing or filing. Choose Edit > Preferences > Document (Acrobat > Preferences > Document on Mac). Select either or both of "Examine document when closing document" and "Examine document when sending document by email."

The Examine Document process gives you control over content removal, but doesn’t let you examine a document that contains multimedia or one containing significant edits. For example, if you’ve added, removed or changed multiple renditions of multimedia content, Acrobat stores extraneous information about the renditions and changes. While you may need that information during your project development, you don’t need it in the finished file.

Choose Advanced > PDF Optimizer to open the dialog box. The first step is to analyze the document to see its contents. Click Audit Space Usage to examine the document and generate a report (Figure 4).

Figure 4: Review the document’s components before optimizing.

The report lists the percentages of the entire document size and size in bytes for elements such as comments, form fields and images. In the example, the fonts use nearly 65 percent and images nearly 30 percent. Click OK to close the audit report.

Configuring options

The default settings for optimization in the PDF Optimizer are the same as those of the document. If you click the Make compatible with pull-down arrow and choose another program version, the Settings name in the upper left of the dialog box changes from Standard to Custom, as shown in Figure 5.

Figure 5: Review the document’s components before optimizing it.

The column at the left of the PDF Organizer lists the optimization categories, shown in Figure 6. Click a category label to display settings at the right of the dialog box. The optimizing options vary according to the program version selected in the Make compatible with list.

Figure 6: Customize settings to balance document quality against file size.

Here are some common types of optimizing to consider:

  • Specify settings for images in your document, including color, grayscale and monochrome images. You can define compression types, quality and downsampling values, terrific for saving a copy of the file for quick webpage downloading.
  • The dialog box lists all fonts used in the document. Unembed fonts you don’t need embedded, such as common and system fonts.
  • By default, the Transparency settings aren’t active in the PDF Optimizer. Depending on your document contents, choose transparency flattening and settings, such as resolutions for text, line art and gradients.
  • Select objects to remove in the Discard Objects settings. You can select objects such as form fields, alternate images and search indexes.
  • Decide which user data objects to remove, such as layers, form content, cross-references and comments on the Discard User Data pane.

    Note: The Discard Objects and Discard User Data panes list the objects evaluated by the Examine Document process.

  • Choose commands from the Clean Up Settings pane to take care of other cleanup details, such as removing invalid links or bookmarks, encoding options and a method of compressing the document’s structure.

When you’ve finished choosing optimization settings, click Save to close the dialog box. Name and save the optimized file.

Check the effectiveness of your optimization by reopening the PDF Optimizer and re-running the audit. Optimizing the example file (audit results are shown in Figure 4) using the default Acrobat 8.0 and later compatible settings achieved an enormous file saving. Images dropped from 37kb to just over 9kb, while fonts dropped from 84kb to less than 2kb. The overall file dropped from 128kb to just under 20kb.

Reusing optimizations

You don’t have to configure PDF Optimizer settings each time you optimize a particular type of file. Once you’ve chosen settings, click Save on the PDF Optimizer dialog box to name and save the settings. The next time you prepare the same sort of file for distribution, choose Advanced > PDF Optimizer to open the dialog box, click the Preset pull-down arrow and choose your custom settings. Click OK to process the file.

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Products covered:

Acrobat 9

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Scan and Optimize

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