What does this have to do with WordPress?
Everything,
My site sometimes includes links to pdf file of interest but it tries to open them in the browser. I want the user to download them instead.
This happens because most plugins or handlers installed for .pdf files are set by default to open .pdf’s in a browser window (Adobe reader, for one), then give the viewer the option to save a copy of the document locally. You can compress the .pdf and offer the .zip for download. Zip files usually open a dialog for the user, and asks if they want to open or save the file, as opposed to the pdf plugin that usually just opens the document. I think you could also force the download via javascript, but that will indeed require some code editing, and I question how safe it may be. If your http server is under your complete control, you may be able to force the pdf to download by changing your mime.types configuration.
