In the HTML version of the manual, as shipped in the pocket-reform-handbook, it appears a lot of the referenced illustration image are missing.
Example of a missing file:
/usr/share/doc/pocket-reform-handbook/html/_static/illustrations/input-pocket-keyboard-eurkey.png
Thank you for your bug report!
This is a known problem and also the case for the handbook of the big reform. Example of missing file: /usr/share/doc/reform-handbook/html/_static/illustrations/9-flashing-the-firmware.png.
The problem is, that debian/rules does not call this script: src/make-pngs.sh · main · Reform / MNT Pocket Reform Handbook · GitLab
This problem is fixed in the version of the handbook that I will upload to unstable after the handbook of the big reform has been accepted by ftp-master. I thus did not bother and updated the packaging in the MNT gitlab. I hope this will be fixed soon. If you have some favours to trade with ftp-master, now would be the time. 