Help, how do I convert something I edited back into a PDF losing all the other pages?

[Blighty]

(02-20-2019, 07:07 AM)Frus8edDude Wrote: Worked great, only one hitch, since my pages aren't all the same length/height it fills the extra space with white.
....but after I edit and export I'm left with those extra white boxes.

I don't know how to fix that in Gimp. Maybe someone can help.

All I can think of is set up a document in Libre Office or Scribus. The size of individual pages can be set. Then copy the edited images from Gimp and paste them into that document and export from there.