Swift iOS PDFKit - Resize each document to A4 size

Hello. Attached is an application that contains 3 PDF documents. The app will load with the first document which is A4 size. The second and third documents are added when the user taps "Insert documents". I have attached a video demonstrating this. I would like the second and third document to be A4 size, which is the size of the first document that is loaded upon the app launching. I would like the second and third documents to appear as the first one. For documents that have dimensions larger than A4, they will need to be resized so that they fit within the A4 dimension bounds. Something similar to this stack overflow Q&A: https://stackoverflow.com/questions/71468302/converting-images-to-a4-size-pdf-using-swift

Budget is £50
I look forward to hearing from you