The following elements can not be compared or have limited comparison capabilities.
Diagrams will be compared as composition of lines and text
Technical drawings will compare each line separately, parts and components cannot be identified
Line Breaks between words - PDF has no line break marker or paragraphs; the comparison will not assume whether a line break is intentional or the result of a paragraph margin; use 'strict' comparison to find all line break differences(automatic and by user)
Changes to the page margin / indentation - PDF has not margin and indent markup; a different horizontal location of text will cause no difference
Changes to the glyphs of fonts with the same name - if the fonts in the compared files have the same name; the comparison assumed that their visual appearance is equal; the visual appearance of each single character will not be compared
Recognize fonts as equal, if the name can not be matched - if compared fonts have a different name, it will be a difference event if the visual appearance is equal; applies especially to embedded subtypes
Moving text or other objects to a different position in terms of content - PDF has no entities like text boxes; so a moved object (table, text box) is a major differences for all contained atomic element
Images: changes in image effects - Only the actual visual appearance is compared
Images: uncompressed vs. highly compressed - Jpeg compression can lead to extensive artifacts which will be recognized as difference when compared to uncompressed formats