Try this:
Open three paintbrush windows.
In the first one, open up
obverse picture. Hit ctrl+a to highlight all then ctrl+c to copy.
In the third one, hit ctrl+w and expand the size by 500 in each
field. If you can
still see gray, do another 500.
In the third one, hit ctrl+v, which will paste your
obverse.
In the second one, open up the
reverse. Hit ctrl+a to select all then ctrl+c to copy.
Back to the third one hit ctrl+v and then move the pasted
reverse next to the
obverse rather than on top.
Use the selection tool to crop the photo. Hit ctrl+c to copy.
Open a final new paintbrush and hit ctrl+w, reduce size to 10 in each
field. If the white square is smaller than your photo, you’re
fine. If not, reduce size again.
Hit ctrl+v, then save.