02-20-2019, 02:46 PM
I think it is this: The first page is horizontal and that sets the canvas size. Vertical pages are therefore truncated.
All the pages need to be the same orientation - horizontal
Open the PDF as images, then rotate the vertical images to horizontal Image -> Transform -> Rotate
Then a choice, and for a beginner the safest might be save each image as a gimp xcf. Then, starting afresh, File -> Open as Layers all the .xcf files. That gets a stack of layers. Now Export as a PDF.
The other way is moving the images into a singe image as layers, Edit -> Copy Edit -> Paste Layer -> To New Layer or click and drag from tab to tab.
A quick 3 minute video of the process that might help https://youtu.be/8mBFaXf8o4U
All the pages need to be the same orientation - horizontal
Open the PDF as images, then rotate the vertical images to horizontal Image -> Transform -> Rotate
Then a choice, and for a beginner the safest might be save each image as a gimp xcf. Then, starting afresh, File -> Open as Layers all the .xcf files. That gets a stack of layers. Now Export as a PDF.
The other way is moving the images into a singe image as layers, Edit -> Copy Edit -> Paste Layer -> To New Layer or click and drag from tab to tab.
A quick 3 minute video of the process that might help https://youtu.be/8mBFaXf8o4U