Selecting the Use Adobe Acrobat option will open the document in Adobe Acrobat. Therefore, this is most likely what is causing the issue.

Please try reinstalling Adobe Acrobat from here.

Are you able to open Adobe Acrobat without using Firefox?

Reinstalled with same results. Here is a site I am trying to download from - tax forms. http://www.rev.state.la.us/Forms/ForIndividuals It does nothing. No new tab, nothing.

I just attempted to download a form from the link above and it was successful on my end.

Is this the only website that experiences these issues?

As a temporary work around, you can right click on the link to the PDF and select Save Link As.... This will save the PDF document to your hard drive and you should be able to open it up from there.

No, but I see there are three Adobe Acrobat forms options in FF Option Applications. Those were the ones I was looking at - once I found the simple pdf option, all is well!!!! Thank you for helping!!

Glad to hear that your problem is now solved. Thanks for contacting the Mozilla support team.