In this post, I want to write about how to replace one page of existing PDF files with a new PDF image.

Crop image and convert it to PDF file

Because the page size of most PDF files is A4 size1. First we need to crop the image to have the same aspect ratio as an A4 paper. We can use FastStone Image Viewer to achieve this.

Open the image using FastStone Image Viewer, press x and we will be in the crop mode. We need to add a new aspect ratio for the A4 size.

In the pop-up window, click “Add” and set the width and height of the paper ratios (see image below).

Then go back to the crop board and choose the ratio we have just set up. Then choose the option “Lossless Crop to File”. In the pop-up save file window, choose the PDF format.

Embed PDF image to the existing PDF files

Now we can embed the produced PDF image to the existing PDF files. We use the free tool pdftk to do this. Download, install it and set the PATH variable properly.

If we have a file Thesis.pdf and we want to replace the 5th page with another file sign_page.pdf. We can use the following command:

pdftk A=Thesis.pdf B=sign_page.pdf cat A1-4 B1 A6-end output signed_thesis.pdf

This command is pretty self-explanatory. We concatenate page 1 to 4 of Thesis.pdf, the sign_page.pdfand page 6 to end of Thesis.pdf to form a new PDF file. In effect, we have replaced the 5th page of Thesis.pdf. The produced file will be signed_thesis.pdf.

Another way to embed PDF files.

If you have purchased Adobe Acrobat Pro, you can use Acrobat to replace a page in PDF files.


  1. The A4 size is 210x297 in mm.