viewing tif files

Hello my iPhone 5 with iOS "7.1" cannot download a "tif" email attachment, it will however open and view a "tiff" attachment, no problems. I can not even save the "tif" attachment for viewing elsewhere. I work for a firm where a fair amount of "plans" have been saved over the years in the "tif" format and it would be nightmarish to open and save thousands of these images in other format. I also tried to rename the "tif" to "tiff" image with still the same problem. Any ideas for this issue?