tiff file cannot have alpha channel or compression
tiff2pdf -p letter -o output.pdf input.tif
tiff2ps
tiff2rgba
tiffcmp
tiffcp
tiffdither
tiffdump
tiffinfo
print information about TIFF files
tiffmedian
tiffset
tiffsplit
split a multi-image TIFF into single-image TIFF files
Adobe Acrobat 6
drag single or multiple .tif files into Acrobat (on the Acrobat program icon), and Acrobat will ask if you want to combine them into a single file
also, File → Create PDF → From Multiple Files… should work
in Acrobat 6, there is a problem with the default order of merging documents and it almost always requires user intervention to put the pages in proper order before completing the merge