There are Kindle readers for just about every device under the sun. What is the reason that you want to convert them? Is it because that the Kindle format isn't all that great for technical books with figures and code? If so, you won't gain much from conversion -- it'll just be the same crappy layout except in PDF format. If you want the tech books in PDF format that mimics the layout of the printed versions you'll need to buy them as PDFs in the first place.
I found the Kindle approach too restrictive (like charging a fee to get PDFs from other sources on the device), so I stuck to getting PDFs for reading on a 7" Android tablet. The Kindle sounds like a better device for reading, but the tablet/PDF approach works well for me, and it's one fewer device. Obviously, YMMV.
The knights of nee want a shrubbery. And a tiny ad: