Originally Posted by mike_smith
Can you convert a pdf to MOBI to avoid the above?
True, but as Avantman42 correctly noted, the results are often poor. In general, you should avoid downloading a PDF when there is a true ebook format available. If there is only a PDF available then I recommend that you first try to read the book as a PDF. If that proves impractical then try converting it to MOBI with Calibre or MobiPocket Creator.
When a book is not burdened with DRM (Digital Rights Management), Calibre can usually convert it to MOBI for use on a Kindle. When the original is a true ebook format (e.g. ePub, FB2, ...) the conversions are usually very good, if not excellent.
Calibre is also a library manager and can do the sideloading to a Kindle, and most other ereader devices, over USB for you. It can also be configured to email ebooks to your Kindle's email account so that they will download when you sync your device over WiFi or 3g (preferably WiFi because that way there's no cost) with Amazon's servers.