I have Adobe Acrobat Reader DC, and I keep trying to type a set of four numbers. Let's say these four are 0067. But every time I click out of the field, it reduces it to just 67. I need to have all four digits show up on this form. Is there any way to fix this annoying formatting?
You can't change this with Acrobat Reader.
Report the issue to the authors of the form. They need to fix it for you,
by changing the Format setting of the field from Number to None.