normaly, if you import tiff and pdf by using the client, and the proper setting is set, these format should be index for the content by using the text file create by the OCR, or the pdf iFilter.

for ms office documents , it should be extracted text when import documents

if it does not work, you can create a workflow to find all document that do not have a text attached to them and create asdk script to do it.

or you can by using the client do the same kind of serach and start an ocr process to extract the text.

both will index the content of the documents.