Rather than
pdf, consider ... LOT more compact
How PDFs are made will effect their size.
On the moremanuals site I found some files
like m3100ma1.pdf at 800+KByte/page
and others, like SC41MS.pdf at 12-KBytes/page
it depends on the tools and care used.
Very true. I like DjVu, and was the source (I think)
of Boris finding out about it...
But I still prefer PDFs. I scan text-only pages at
600dpi in line-art mode, which creates hi-res bitmaps
instead of greyscale files. While intuition might say
that greyscale is better, when printed, most people
will not be able to tell the difference.
For pages with extremely detailed info, I use 1200dpi
line art; for photos, I use greyscale, and do my best
to clean them up. Halftone images require de-screening.
-dq