Originally Posted by
LordEntrails
The 5E PHB is encrypted and can not be modified directly. You can though use it as a basis for creating your own PHB, but you will have a lot of work. I can think of 2 ways;
1) Create a development campaign, in that load the PHB, copy the entries you want, modify them. Export to module. Whenever you want you then will have to load both modules in your play campaign and know to use the modified entries since the originals will still be there.
2) load the PHB in your play campaign, unlock and edit the desired entries. This method will not allow you to transfer (easily) these changes to other campaigns.