scan to pdf

some scanners use jpgs for each page when scanning to pdf. i've found it works better to scan to a mtiff and then covert that with
tiff2pdf -o output.pdf input.tif

i got pretty good results in terms of size and readability with 300dpi, medium quality, black and white.

i've tried encrypting the pdf, and it all works, except that on the kindle it won't let me do any annotations on an encrypted file, even when I try to allow it explicitly:
pdftk in.pdf output out.pdf user_pw foo owner_pw bar allow AllFeatures

all annotations, etc, work fine on the desktop so i think it's an issue with the kindle acroread. at least i can work with it after decrypting, kindle or elsewhere
pdftk encrypted.pdf input_pw foobar output decrypted.pdf