There's no special feature for comparing PDF files. However, you can try comparing them by using approaches described in this article.
Also, you can consider the following possible solutions:
1. Converting a PDF file to text (by means of a PDF viewer) and comparing the resulting file with a baseline text file copy.
2. Copying the needed part of a PDF document to the clipboard and checking Clipboard Property's value.
BTW, in our DB, we have a suggestion to implement special support for PDF files, and your post has increased its rating. Thank you.
Essentially, what Alex responded with is how you would go about doing that. There are a variety of ways of examining what's in the PDF and comparing them to an expected set of results. There's no "native" way of getting to the PDF, you'll need to follow one of the processes that Alex mentioned.
Personally, I used the MSAA method described in the article Alex linked in which works very well.
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