>>876452.pdf files work on most readers (the Paperwhite too) but either look horrible and/or are slow as fuck to navigate. BUT you can make it work by converting them back to a regular e-reader format. It isn't usually encouraged to use PDFs as source for such conversion (other e-reader formats like MOBI, EPUB, LIT or simple HTML and even Word files are preferred) since according to the manual of i.e. Calibre (which I use to convert all the stuff I get from all kinds of dubious sources) PDF is the worst format to reflow text. But beside some problems generating the table of content from a PDF (which can be fixed manually or with some options of Calibre) and some issues with weirdly formatted PDFs with strange letter spacing and sometimes unnecessary paragraphs I could convert most PDFs just fine back to the native e-reader formats. Again Calibre is the weapon of choice to do so.
I too got a Kindle Paperwhite, despite already knowing that Amazon used their own proprietary (pretty castrated and bad) e-reader file format (AZW and AZW3). The de-facto standard EPUB files, that most other non-Amazon devices use natively, aren't supported by the Kindle devices at all. Even without Calibre you can convert some formats (like PDF or Word) using the associated kindle e-mail address you get with the kindle. But I don't trust this conversions, since you can't preview the result or have any conversion options (which you have plenty with Calibre). But I got a Paperwhite anyway since I wanted to sync my bookmark after reading the same book on my smartphone (Kindle App) and I don't know if this works with the alternative readers too. The only catch with the Kinde devices is, that you have to use a rather outdated e-reader format for this feature (either the proprietary AZW (but not AZW3) or MOBI).
I only have one book on the Kindle that I actually paid for, the rest are mostly pirated books that I converted with Calibre (mostly from PDF or EPUB) and send to the Kindle via Mail.
