The Image Downsampling tab is used to control the size and quality of any images (such as pictures, screenshots, company logos) in the PDF file, which can help reduce the final size of the PDF. This tab is only available if the output type is set to Adobe PDF on the Save Options tab; not available if Create each page of the PDF as an image is enabled on the Save Options tab.
Downsampling can be enabled or disabled and set to different levels for color, indexed, greyscale and monochrome (or black and white) images. By default, downsampling is enabled and set to 150 DPI for all 4 image coloration categories.
The downsampling DPI can be set any where between 50 DPI and 2400 DPI by typing the desired level into the edit field, or using the plus and minus buttons to the right of each edit field to set the value.
Images will only be downsampled if the DPI of the image is greater than the requested DPI. If the DPI of the image is already less than the downsampling DPI, the image is not changed.
See Also: Reduce Searchable PDF File Size