Kindles are very good for packing a stack of documents into a lightweight device but not everything comes in PDF format. Sure, you could send an e-mail to your personalised e-mail address for your Kindle and have your document (of a supported format) converted and transferred to your Kindle over 3G for a fee but it’s so easy to do it yourself for no cost at all.
Perhaps the most labourious part is converting your documents to PDF. The easiest approach for almost any document is to use CutePDF Writer previously covered here. Of course, Office 2007 and 2010 include the ability to save PDF natively which might save you having to use a third party tool. After that, all you have to do is transfer the file to your Kindle by plugging it in, browsing to the “documents” folder on the device and copying in the PDFs. Next time you start up your Kindle, it should recognise your documents.
I use this to take all of my university documentation with me so I can read up on the go.