With the lastest OCR API and Online OCR update, we added support for multi-page TIFF/TIF files. Now they are processed the same way as multi-page PDF documents. You can test the multi-page TIFF support directly in the online OCR form.
How to OCR a single page or a multipage TIFF file
The multi-page TIFF support is built directly into the OCR API. New command is required. The API recognizes multi-page TIFF files automatically. OCRing multipage tiff images is now as easy as doing PDF OCR. The resulting text is subsequently returned in the API JSON response.