As we know that your Kindle (or Kindle app) has its own email address, meaning you can send any PDF straight to your device just by attaching it to an email. (You can find this address in the Kindle's Settings area.)
Unfortunately, most PDFs arrive exactly as they are: static images that aren't optimized for Kindle viewing, and therefore require a lot of zooming and scrolling. If you ask me, they're almost unreadable in this state.
But here's a little-known fact: Amazon will convert your PDF to raw text when you put the word convert in the subject line of the email.
There are a few caveats here. First, the conversion will take time. I sent a few documents through to the Kindle app on my tablet, and although they were just a few pages apiece, it took close to an hour for them to arrive.
Second, this won't work with all PDFs. One of the documents I sent through ended up as a rotated image with each page split in half—and I couldn't even zoom it.
So, I have software that converts the PDFs into kindle format. I can provide you the sample attached.