I have some handwritten notes that I created using an e-ink tablet (Boox Tab Ultra) and that I converted to PDF format. This produces a PDF file where the pages are the size and shape of the tablet screen, which is very different from an A4 page since it is a 10,3'' tablet.
I would like to add these pages to a book in PDF format, in order to print the resulting file later. However, since my handwritten pages look different from the usual A4-sized PDF pages of the book, I would like to convert them to A4 format (I believe that joining two of my pages together vertically, just as they appear in the PDF I currently have, would roughly give A4 size). Is there a way to do this, and for the pages to be resized accordingly to fit exactly an A4 page if there is a slight difference in size when joining two of them vertically?