Does it help if you change the setting to "Always ask" or "Save File" for the PDF file in "Tools > Options > Applications" and open the saved file in the Adobe Reader?

• http://kb.mozillazine.org/File_types_and_download_actions

Changing the setting to "Save File" worked, Thank you!

there is something with the pdf itself that is stopping FF from opening it, as when i try opening the same in Crome ... there also i encounter the same problem (the file opens partially and then stops opening). But if i download the same then i can view the same in Acrobat reader properly.

May be the way the pdf was created used something which FF s not able to render (the graphics used in charts etc)

The work around that is available is that you download the file and save it somwhere, then open the same in Acrobat reader separately