Best practice: Be up-front about what type of document is linked

In almost any situation where you are making a link to a PDF that lives online, give your readers a little tip-off that the link leads to a PDF. Same goes for other non-webpage-type documents: put the file type in parentheses after the link, and note the file size if it is a large file. Like so:

• The IRS website provides printable forms like the popular Form 1040 (pdf).
• Fill out the Library Card Application form (pdf).
• Get to Know Excel 2010 (pptx, 36MB) teaches spreadsheet skills.

But wait, you say! If people know in advance that they'll land on a PDF (or CSV, or PPT, etc.), they might not click that link. And you would be right; however, people who have to be fooled into clicking a document link probably still won't read the document, plus they will be annoyed (or confused) while waiting for it to load.

Being up-front about what you are linking to helps your readers make an informed decision to download the linked file or not. If they are interested enough, they will!