As for feats, I haven't decided. I'm tempted to make an optional sheet for recording them in detail, but I'm not sure that's necessary.
As for the fighter that takes seven feats, it is possible, but also very unlikely that they won't ever opt for an ability score increase. If I can find a comfortable way to fit seven, I'll do it. But I won't go through too many contortions for an extreme edge case.
Yes, with so many optional features and different possible levels of complexities of the same kind of thing (e.g. one-line feats vs long descriptions / multiple abilities feats), it is harder than ever to design character sheets
On one hand, the optional stuff would make more sense on a separate page. On the other hand, you don't need a whole page for feats for instance...
Maybe there is something else than PDF that lets you hide/expand with a click certain sections of the document, before printing?
Shield is misspelled in the AC subsection.
I would like another line for languages.
I would also prefer if the sheet were editable.
Thanks for the update--just in time for tonight's game!
I second the languages suggestion--it's very easy to start with 10 languages if you're a high elf sage mage. They don't really need to be on page 1 (they don't come up as often as hit points or class abilities).
The formula for Save DC on the spell sheet is wrong: it should be 8 + magic ability modifier + spellcasting bonus (if any). Not all classes get a spellcasting bonus, and even the classes that do have one don't get it all the time. You might want to think about having "with spellcasting bonus" and "without spellcasting bonus" boxes, since it can vary from round to round.
Some feedback from my players: they find it annoying to have to turn the sheet over to look at their limited use features (ki points, superiority dice).
On the other hand: they need more slots for limited use features. The Fighter has second wind, action surge, and superiority dice.
In the armor section (on the right side of the page) I'd change "bonus" to "AC," since a suit of armor doesn't give you a bonus, it just sets your AC to a certain number. If the column is just labeled "AC," someone can truthfully write that chain mail is AC 16, and a shield is AC +2.
What's the deal with the "wounds" box next to hit points? It should just be called "current hit points." Calling it wounds makes me think of Warhammer.
What's the "other modifiers" column on page 1 for?
The "Ability Checks" header seems misnamed, since it encompasses proficiencies (which include skills, attacks, and saving throws).
Attached is an edited version, which I will use for the time being.