This free, open-source program installs a new "printer" on your computer that will convert a file in any program that you can print from into a PDF file and then save it on your harddrive.
It is very handy if you want to send a document to someone exactly as-is so they can read it no matter what program you used to create the document or what fonts or pictures you used. Sometimes, sending a file to someone, even if they have the same program, can cause some viewing errors. If they have a different program, then the possibility of viewing errors increase.
PDF files do not have that limitation, however. The only limitation is the person who receives a PDF file cannot edit the file, but they can open it, read it, and print it.
PDF Creator runs on Windows.