About optimizing a 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.

Reduce icon Select Home > Tools > Reduce > Optimize for a dialog box with the following panels.

General panel

First, specify the compatibility level and select from compression options.

  • Optimize PDF for fast web view: Objects are prioritized so text displays quickly, followed by pictures.

  • Use Flate: Apply settings in the Use Flate section to encode non-encoded streams that are used instead of LZW to reduce stream size.

  • Remove: Apply 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.

  • The Discard all section offers options to remove certain elements:

    • Comments: Delete all comments added to the PDF. Comments include 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.

Images panel

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 bigger file sizes if the original image was compressed with JPEG.

JBIG2 compression is best for black and white images. If image quality is less important, use downsampling to reduce the file size.

With scanned pages, the Use MRC Layers option splits the image into three layers with optimized compression for each, so the total file size is reduced. Deskew is useful for images scanned at an angle. Despeckle eliminates spots and shadow lines from scanned pages.

Select "Optimize images only in case of size reduction" to have the facility inspect each image in the document and leave images untouched if the optimization will not result in a smaller file size.

Fonts panel

Unembedding a font reduces file size. But the new PDF file may differ from the original; if the viewing computer does not have a required font, it must be substituted by a similar or more basic one.

Another way to reduce file size is by Reducing the PDF.