Converting PDF to TIFF

In addition to the good information above, there is no such thing as a multi-page tiff AFAIK, however you can convert the content of a pdf into an image and keep it a pdf using a preflight profile. Tools> Print production> Preflight> Fixups. Although preserving the vector pdf content is usually preferred. If you are trying to create two pages side by side, place the pdfs into an InDesign page and export to a pdf, then convert to a tiff in Acrobat.

I am pretty sure that Acrobat doesn't know how to make a single TIF document (or any bitmapped document) from a multiple-page PDF. Consider that it may not know if you want them above and below, alongside of each other, or on the diagonal.

Once they are TIF, if you have access to any image manipulation application (e.g., Photoshop), you can set them the way you want.

This is correct. You will get 2 TIFF files for 2 pages.