I have an azw3 as described above. It can be converted into epub, using the extension from Calibre "Kindle Unpack", but there are no paragraphs, meaning that the all the words in the txt file is structured like a wall of text. I use SumatraPDF which can read all the azw3, mobi, pdf and epub2 and/or epub3 files with much less effort than Adobe Reader.
Edit: Oh, I forgot to tell you. The azw3 file can also be unpacked into xhtml files.
I see two options for you:
AZW3 is just a slightly modified MOBI format. So virtually any (on-line or off-line) solution that can do MOBI -> PDF conversion (with results acceptable by you) should do the trick.
Since you can already open AZW3 files directly in SumatraPDF then I consider installing a virtual printer driver that will be able to print anything (from screenshot, image, webpage through any open document) to PDF format. And in most cases (there are many, many options for virtual printers) it will do 1:1 or rather to say WYSIWYG, so with all the formatting etc. intact.
I have never used any of above approaches so this is theoretical suggestion only. But, my friend told me that first options works just fine, only he had to change file name's extension from AZW3 to MOBI to "foul" such on-line converting service.
