With JavaScript, I think you can use the toPDF converter (may be wrong, might need a plug-in). That would convert a one page TIFF to a one page PDF. Then you would combine the PDFs, by opening one and inserting pages of the other, and save. Really far from ideal, but possible.
Bear in mind Acrobat is designed for light duty automation. Close and restart it at least every 100-200 files, perhaps more often.