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Your only options are Primer, which works very well but is expensive and hard to find
You can
download Primer here. Unfortunately, it's no longer supported by the company it was sold to, and you need a serial number to run it. Google is your friend, though...
Primer works quite well, though it's a bit slow and cumbersome, and you'll do a lot of scrolling back and forth. If you have text only files, converting the pdf to mobi is a better choice
(google Auto kindle
), but if you need to see graphics in the pdf, or see them from the web when you're away from your PC, Primer is probably the best option.