How to read PDF from web site ,update the same pdf and save.
In order to change the default reader for PDF files follow these
steps (This is if you would like to use Firefox’s built-in PDF reader):
Go to Tools > Options (or Firefox > Options).
In the Options window, select the Applications tab.
In the Search field, type PDF. You should find Portable Document Format (PDF).
On the right handside you should find an Action column. Use that to select your favorite PDF reader. In order to view PDF files in Firefox, choose Preview in Firefox.