FYI, using the Mod_Rewrite Variables Cheatsheet makes this example, and all advanced .htaccess code easier to understand. This demo lets you set a cookie with 1 of 3 values, then you just request the pdf file with a normal link click and get 1 of 3 different responses. This is accomplished with a nice bit of .htaccess code.

Set PDF Viewing Mode - Make a selection, then click the view pdf button.

Inline Download Save As View PDF using selected mode »

Htaccess