Option 1
Send an email to pdf@koolwire.com and include your file as an attachment. In a few moments, you’ll get an email response from KoolWIRE with a new attachment containing your file in PDF format. Its a free service and KoolWire can convert Word (.doc), Powerpoint (.ppt), Excel (.xls), Jpeg, GIF, Rich Text Format (.rtf), and text (.txt) files to PDF.
Option 2
You can do the same thing by uploading files to free file conversion services (i.e. Zamzar).
Option 3
For SOME documents, you can use the free Google Docs & Spreadsheets.