Heroes V version 3.1 - Official Manual EN, CZ, PL
EN+PL Mirrored from h5.heroes.net.pl, which was recovered from heroes-fr.com, which is gone. CZ Mirrored from heroes-centrum.com. This one is having Ubisoft Seal of Approval.
CH - Scripting 2.1
A lot more talking about scripting and modding is available in here.
At these times CH also created it's own guide and manual, which you can take a peak here. However it's obsolete and was no further updated.