If you want simple PDF files, CutePDF or PDFCreator work OK, and simply
Watch out for the junk software that both include - make sure you untick the optional toolbars and speedup software...
both are free
however both, like virtually all of the non-Adobe programs are not native typesetting programs - they simply convert from other formats
If you have heavy typesetting work to do -e.g. for getting a book ready you may need to purchase a copy of Acrobat......yes I know its expensive
But not all PDF files are the same.......
However, don't forget that recent versions of MS Office have PDF creation capabilities. For Office 2007 its a free plugin download, for 2010 and 2013 its built-in. That has reasonably tight integration and if used (for instance) with MS Publisher may give you the proof-ready galleys I think you're going to need for your book. Publisher can also output to Postscript - which PDFCreator can convert to PDF
As far as Kindle goes, start here
https://kdp.amazon.com/self-publishi...A37Z49E2DDQPP3
What format are the documents in currently?