You can not do that using Adobe Acrobat 9. Adobe never made a create PDF add-on for Firefox for use with Adobe Acrobat 9. They created a Firefox add-on for use with Acrobat X, but currently that one does not work with Firefox 4 though Adobe are working on an update.

Thank you, Tony E, for saving me from wasting my time with hit and miss and hunt and peck efforts to solve the unsolvable problem.

Amended reply:

It appears that Firefox has gone sideways concerning a PDF printer. After installing Firefox 4.0.1 and finding no Adobe PDF printer available, I went to my Windows 7 Control Panel > Programs and Features > (my version of Adobe Acrobat) > selected my version of Adobe Acrobat for re-installation.

After that re-installation was completed (luckily Adobe had just recently performed an online automatic update of my version of Adobe Acrobat; otherwise, I would have likely been forced to pin down and install any updates to the re-installation of an an older version of Acrobat ), an Adobe PDF printer was added to my Firefox list of printers. Unfortunately, my first crack at using that Adobe PDF printer failed with an error message indicating that Adobe Acrobat Create 1.0 did not work on Firefox.

But what the Firefox print list did have was a printer labeled "DocuCom PDF Driver." So, I selected that DocuCom PDF Driver and, poof, that selection saved all the text of the web page I wanted converted to a PDF file (but without most of the graphics), which is almost all that I wanted anyway, and, as a bonus, that conversion created an Adobe PDF file (but without interactive features, which is what I did want and which my copy of Adobe Acrobat Pro Extended is capable of creating .)

And after that Adobe PDF file was cranked out, I tested the Firefox print feature again, but this time selecting the Adobe PDF printer from that list for conversion of a web page to an Adobe PDF file and, poof, that Adobe PDF printer is now operational (but again without creation of a PDF file with interactive features).

I just cranked out another Adobe PDF file of this Firefox web page upon which I am preparing this reply, using the Adobe PDF printer from the Firefox list of printers (ignoring the above-described error message), selecting the Adobe PDF setup icon indicating that an Adobe PDF file was ready for saving, and then saving the file.

End of story.

Update: Adobe PDF printer in my Firefox is working fine, bizarrely, now working with full text and graphics conversion, but still no interactive feature within a PDF file as provided by Adobe Acrobat Pro Extended.

There is an Abode PDF printer driver that can be used with any application, but the create PDF add-on goes further, it will convert a web page to a PDF file keeping the links intact, the PDF printer option does not create links.

Thanks; I know, but I was not able to even generate a PDF page of any kind on Firefox until I tinkered my way into generating PDF pages as previously described.

If the create PDF add-on is an app, I don't do apps. I treat apps as a virus and scamware. I have no idea what I am getting underneath an app's exterior veneer of legitimacy.