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Optimize PDF

To optimize a PDF, you can create a copy of the file with changed properties that are more suitable for particular purposes. This approach gives you the ability to balance file size against display quality. The Optimize PDF tool handles images and other document elements, such as comments or JavaScript.

To optimize your PDF:

  1. On the Convert toolbar, select Reduce (Reduce icon) to display the available tools, then select Optimize PDF.

    The Optimize PDF dialog box appears.

  2. On the General tab, select the preferred PDF standard in the Compatible with list.
  3. Optionally, select Optimize PDF for fast web view. This option prioritizes objects so text displays quickly, followed by pictures, which is optimal when reading long documents online.
  4. To reduce stream size, adjust the settings in the Use Flate section to encode non-encoded streams that are used instead of LZW.

    LZW (Lempel-Ziv-Welch) compression was widespread for PDF streams up to PDF 1.4. Flate (DEFLATE) offers better compression ratios and is the preferred method in newer PDFs.

  5. Optionally, adjust settings in the Remove section to clean the document structure by eliminating tag information. You can remove private data from other applications, embedded thumbnails and invalid bookmarks and links: these items may be useless and they do not affect the appearance of the PDF file.
  6. Optionally, mark miscellaneous elements for removal in the Discard all section:

    • Comments: Delete all comments, including notes, markups, drawing objects as well as file and sound attachments.

    • Form actions, JavaScript actions: If the PDF has interactive features that are not needed (such as buttons for sending a form), you can delete them.

    • External cross-references: If the PDF has links to other files that will not be available to other users, the links can be eliminated.

    • Alternate images: An image in the PDF file can have "alternate" images that are optional and can be deleted. For example, a color image may have a gray alternate image used for printing instead of the color image.

  7. Switch to the Images tab.

    Images in PDF documents can have different color depth, resolution, and compression. As these factors change, the image and document size varies. So, resampling and recompressing pictures can reduce file size considerably.

    These options change the sampling rates, compression methods, and quality of color, grayscale, and black-and-white images in the PDF. To reduce file size, use JPEG or JPEG2000. ZIP can produce larger files if the original image uses JPEG compression.

  8. In the Color Images section, set preferences for color images.
    1. In the Sampling list, select the method for reducing the number of pixels in the image. For details on sampling methods and quality see Sampling and subsampling.

      • Average downsampling to: Averages the colors of multiple pixels into a single pixel.

      • Subsampling to: Keeps only one pixel from a block.

      • Leave original sampling: Leaves pictures intact.

    2. Next to the Sampling list, specify the target resolution and the resolution threshold. Power PDF resamples only the pictures with a resolution exceeding the treshold.
    3. In the Compression list, select an algorithm.
      JBIG2 compression is best for black and white images.
    4. In the Quality list, select the image quality level.
  9. In the Grayscale Images section, set how to treat images using only shades of gray and no color.
    The settings are the same as in the Color Images section.
  10. In the Black-and-white Images section, set how to treat binary images using only two colors, tipycally black and white.
    The settings are the same as in the Color Images section, except that the Compression list offers different algorithms.
  11. Optionally, select Reset to revert settings to the default.
  12. Select OK.
  13. Follow the instructions on the screen.