I'd to update to Acrobat 9.1...

HCL Notes/Domino 8.5 Forum (includes Notes Traveler)

Subject:

Tried to get the same functionality once with 8.5 and Acrobat 9.
Although I've done everything as documented by Adobe, I did not work.
Found a technote that Acrobat 9.1 is needed, upgraded to 9.1 and it worked.

Here's how I've done it:
Lotus Notes 8.5 is supported since Adobe Acrobat 9, but it actually works only since 9.1.0.
Adobe Acrobat 7 has no Lotus Notes plugin, Adobe Acrobat 8 is supporting only Lotus Notes 5 - 7.
So, if any user wants to create PDFs out of Notes documents using PDFMaker, Adobe Acobat 9.1 or higher must be installed on the machine AFTER Lotus Notes 8.5 has been installed.

The following modifications are done to the Lotus Notes 8.5 installation:

Added files to C:\Program Files\IBM\Lotus\Notes:
AdobePDFMToolbarInst.dll
ndbPDFML.dll

Added notes.ini entries:
AddInMenus=C:\PROGRA~1\Adobe\ACROBA~1.0\PDFMaker\Mail\LOTUSN~1\PDFMLO~1.DLL
AdobePDFMInst=1
EXTMGR_ADDINS=AdobePDFMToolbarInst

As soon as Lotus Notes 8.5 is started, only the entry:
AddInMenus=C:\PROGRA~1\Adobe\ACROBA~1.0\PDFMaker\Mail\LOTUSN~1\PDFMLO~1.DLL
is remaining in the notes.ini.

An additional toolbar is installed: