I want to be able to "Save As" when downloading with Firefox. The only options I am given is to Save or Open. All the previous questions I have seen deal with being able to save to a certain location, and that I can easily set in Firefox. What I want is to be able to change the filename, so if it goes to download "abc123.pdf" I can rename it to "123abc.pdf" when it downloads.

We use a web based application that I have to pull down pdf charts multiple times every day, but the problem is when you go to download a chart, every one is the same name. I can't just save it to the default directory since it will overwrite the previous one or just append a (1) or something. What I have to do now is use the Open option and have a pdf reader open it, then save from the pdf reader giving it a unique filename, which is extra steps that I do not have to do when using IE, Opera, etc. since I can do a Save As from those and rename it before it downloads.