Append an existing PDF to a PDF template.

To add a static PDF page into a PDF template. This can be achieved by <pdfset> tag.

Add required file into file cabinet.
Navigate to Documents> Files> File Cabinet
Open the folder “Templates”.
Then open the folder “PDF Templates”.
Click on the button “Add File” on the top left corner.
Select the particular file and click open.
Now the file is added to the PDF Template folder.
Click on “Edit” beside the particular file.
Check “Available without login” checkbox.
Copy the URL in the file.
Then click on save.

Navigate to Customization > Forms > Advanced PDF/HTML Templates
Click Edit beside the preferred Advanced PDF/HTML Template.
Insert a <pdfset> tag before the first <pdf> tag in source code
After the </pdf> tag 
Add <pdf src = “Paste the copied url from the file” />
</pdfset>
Replace the '&' with '&amp;' while pasting the URL into the template source code.