To add pages to a PDF file, you can use the insert or pages option. Depending on the program you use, you can select another PDF to add, drag and drop the PDF document, or upload the file to Adobe cloud storage. Here are some step-by-step instructions for adding pages to a PDF using Adobe Acrobat:

1. Open Adobe Acrobat.
2. Click on "File" in the top left corner of the screen.
3. Select "Open" and choose the PDF file you want to add pages to.
4. Click on "Tools" in the top right corner of the screen.
5. Select "Organize Pages."
6. Click on "Insert" in the top left corner of the screen.
7. Choose "From File" or "From Scanner."
8. Select the file you want to add pages from.
9. Choose where you want to insert the new pages.
10. Click on "Insert."

You can also use other programs such as Nitro PDF or SmallPDF to add pages to a PDF file. I hope this helps!