Converting TIFF to PDF has many advantages and one of them is that you will not have to worry about attaching an image that weighs a lot, since the PDF format is definitely more optimal to send photographs, without losing quality.
In fact, even in the event that the resulting PDF you get weighs more than you would like, you will always have the possibility to compress it so that it takes up less space. As you can see, there are lots of advantages, when it comes to comparing TIFF and PDF files.