Help with Preview!

I have two questions about preview:

1) Whenever I choose to open a .pdf file from a website with preview, it not only opens the file for viewing but also saves it to the desktop. Sometimes I just want to view the file with preview but not have it saved to my desktop, is this possible?

2) Some files that I use for school do not work well with Preview and only work with Adobe Acrobat Reader. When I download a .pdf file I am asked whether or not to "save as..." or "open with...". However, under the "open with.." option there are no other programs available except for Preview (default). I would like have the option of opening with Preview or Adobe Acrobat but it seems like there is no way to do this. Is it possible? Any help is appreciated, thanks!

 

for question one... I don't want to save the file. All I want to do is have it open without saving.