PDF to TIF conversion can have two purposes. First would be to recover a TIFF (.tif, .tiff) image embedded inside the .pdf document, in which case you should look for a graphics editor that supports import of PDF documents.
The second would be to create an image of actual PDF document. In this case special utilities that can print individual pages from a .pdf document would be the best choice here. They usually offer several output graphics formats choices, including TIF.