VS 2019 Copy part of a pdf and stamp onto another one

Hi

I need to grab part of a pdf and stamp it onto another pdf.

I'm using itextsharp in vb.net to:

1. Resize the 'from' pdf to a new 'crop' file with cropbox, mediabox etc set to the area I want to grab
2. Stamp the 'crop' file on to another pdf at specific cor-ordinates

This works to an extent, but the crop file still contains info I don't want, so when I stamp it on it adds some text from the original in a hidden layer on my new pdf.

I've done a lot of googling today trying to find a way to remove hidden info when I resize a pdf, and it seems it's just impossible without using Acrobat.

So I need another approach to this. Is there way to only grab part of a page when I use GetImportedPage and AddTemplate to stamp?

Thanks for reading - happy to post code of what I've got so far but it's a bit of a mess!