Recently a patron emailed libref with a problem opening JSTOR docs. She had the most recent version of Acrobat. Turned out that the following tips worked.
1. To work around this problem, right click on the PDF link and open in new window, then right click and save the actual PDF to your computer.
2. Open Acrobat Reader and uncheck “Display PDF in browser” ( Open Acrobat ->Edit -> Preferences -> Internet ->). This will cause any PDF to prompt the user to open the PDF with Acrobat (which will work fine) or save the PDF on the computer