Tapping this button multiple times is not good. It creates several documents in an undefined state.

There is a slight delay from tapping the "Create Document" button until the document have been fully created in the file system. A blocking mechanism is needed. That stays invisible if the document gets fully created within a reasonable amount of time. Otherwise a HUD is to be shown. Or an error message.

This is what it looks like when I'm using an ApplePencil and create documents rapidly.