Adobe Acrobat XI - Manual (Page 207)

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Editing PDFs
Last updated 1/14/2015
To optimize several documents at the same time, use the Output options for the Actions Wizard.
PDF Optimizer options (Acrobat Pro)
Use the options from the panels in the PDF Optimizer dialog box to reduce the size of a PDF.
Images panel
The Images panel of the PDF Optimizer lets you set options for color, grayscale, and monochrome image compression,
and image downsampling.
Specify the following options, as needed:
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 with a size less than 16-by-16 pixels are not downsampled.
Compression Reduces file size by eliminating unnecessary pixel data. In general, JPEG and JPEG 2000 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 Distiller, is superior to CCITT.
Quality Available only for JPEG and JPEG 2000 formats. JPEG and JPEG 2000 compression methods are typically lossy,
a process that permanently removes some pixel data. You can apply lossy JPEG or JPEG 2000 compression to color
images at various levels (minimum, low, medium, high, maximum). For JPEG 2000 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.
Tile Size Available only for JPEG 2000 format. Divides the image being compressed into tiles of the given size. (If the
image height or width is not an even multiple of the tile size, partial tiles are used on the edges.) Image data for each
tile is individually compressed and can be individually decompressed. The default value of 256 is recommended.