If you rely on a Kindle (or Kindle app) for reading, you probably know that it supports not only ebooks, but also PDFs.

In fact, if you've done your homework, you also 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.

For stubborn docs like those, you're probably better off with a more robust conversion option, my favorite being Calibre. But if you're away from your desktop, or perhaps your workplace won't allow you to install software, Amazon's own conversion option might just save the day. If nothing else, it's a quick and painless exercise.

Contributing Editor Rick Broida writes about business and consumer technology. Ask for help with your PC hassles at [email protected]. Sign up to have the Hassle-Free PC newsletter e-mailed to you each week.