If you play D&D 5e here are a few pdfs that you can use for additional information for your character. All are fillable. Or mostly fillable.
Somewhere to note all that equipment and loot you are not worried about carrying because your DM does not bother with encumbrance rules.
Character Notes Sheet.
Somewhere to keep track of people you have met, interesting tidbits of information and so forth.
Character Background Sheet.
Somewhere to put all that background information you can generate using Xanathar’s Guide to Everything.