Open a .PDF in Internet Exporer automatically

We are using Adobe Reader 2018.011.20036, Internet Explorer 11, and Windows 7 SP1 64-bit.

Problem:

Our vendor has hardcoded the opening of all PDF documents to
be opened outside of the browser by using the ‘attachment’ option for
Content-Disposition.  This is desired behavior, however, each time an end
user needs to open a document, they have to click a prompt to Open/Save/Cancel
each time – we are trying to determine how to suppress that dialog window OR
how to automatically open the PDF document.  We do not want PDF documents
from this domain (trusted site in Internet Explorer 11) to be opened inside the
browser and we won’t want to have to disable/enable the ‘Adobe Reader’ Add-On
within IE as that breaks other applications in our enterprise.

Options Tried:

We’ve tried importing the two registry entries below however
neither change worked.  The prompt still appears.

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\AcroPDF.PDF.1]

"EditFlags"=hex:00,00,01,00

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\AttachmentExecute\{0002DF01-0000-0000-C000-000000000046}]

" AcroPDF.PDF.1"=hex(0):

Thank you