Where I work, we have an intranet site to keep head office, interstate and overseas branches 'in the loop'. All documents created under ISO2001 - policies, procedures, forms, work instructions, etc are uploaded as PDFs to the intranet site for people to download and read the latest version as required. Things change quickly, so having a print folder full of e.g. policies, may not mean they have the most up-to-date version. We put a watermark on our PDFs that remind people who print them off to check the intranet for the latest version. We create them as PDFs (rather than say, Word docs) as some are derived from Excel, Visio (flowcharts - lots of these) and other software which not everyome may have access to. Plus of course PDFs preserve all formatting, so the 'corporate look' is retained.
I also use PDFs to upload samples of my portfolio to my website.
And some uses you've already mentioned - using PDFs to send docs via email that you don't want reformatted e.g. resumes, and as a nifty way to send files to commercial printers, including fonts and graphics.