To send documents to other people, sometimes it's convenient to send them as PDF files. PDFs can be read on most OSes -- Linux has both acroread and xpdf clients -- and can also be posted on the Web. PDF clients are commonly available, and prevent the recipient from easily modifying the document.
To make a PDF in Linux, print to a ps file (postscript), and then use the ps2pdf utility (from the ghostscript package) to turn the .ps postscript file into a .pdf.
A webpage with step-by-step instructions for this can be found at:
To make a PDF in MS Windows, you can use the commercial Adobe Acrobat package, or the cheaper pdf995 program available at:
http://site4.pdf995.com/download.html.
There are many free ways to make PDF files on a Windows client using the ghostscript package. (I haven't tried any of these, so please write me with your experiences.) One is GhostWord:
http://www.et.dtu.dk/Software/GhostWord/Index.html.
GhostWord is reputed to be moderately hard to set up, but once it is installed, PDF buttons are added to MS Word, Excel, and PowerPoint.
A different approach is to install a fake printer on a Linux server running Samba, and have MS Windows clients "print" to it. This is described here: