I have ran into this problem a few times as well. I am running Outlook 365. Each time I have successfully corrected the problem by changing the default mail program to Windows Mail and then changing it back to Outlook. Hope this helps with Mailbird as well.

Thanks. Noted for future.

When I perform Arrange>Make same height on form fields, is there a way to keep the bottom of the field in place an only change the top of the field?

Thanks for the replies. I reduced the form field heights to get the font to the size I wanted, so all is good.

Issue still appears to exist after updating to build 331.

Version is 8, build 330

It appears that PDF Editor just handles text size differently when the form field text size is set to auto, and the text is larger than it is when filled in with Acrobat. The form is attached in case there is a setting that can be changed.

After a reboot, the issue is no longer occurring.

I have fillable forms that were created in Acrobat DC. When I use PDF XChange to fill the forms, or change a form field content, the font turns to bold. Please see attached screen shot.