Warning/Errors: Adobe XML forms cannot be merged

I have downloaded an Adobe XML file (IRS form) from a government website & without using specific materials, they cannot be merged with other PDF files. Is the below statement directly related to this topic?

Are you sure this is not a file created by exporting form field data to an XML file?

First, use these instructions... Then Merging can begin

ADOBE XML FILE (EXTENSIBLE MARKUP LANGUAGE FILE)

(Internet file- webpage)

It cannot be merged to other PDF files.

ADOBE XML CONVERSION TO STANDARD PDF FORMAT

01) Open XML file with Adobe Acrobat.

02) Left Click on ‘Printer’ icon at top.

03) Set Printer Setting to Adobe PDF.

04) Click on ‘Print’ icon.

05)*Point left cursor to extreme right file icon on Taskbar.

06)'Save As' Window; re-name file to desired Folder location.

07) Click on ‘Save’ icon. Font quality/color loss noted.

     *if necessary

You can create a portfolio.

LiveCycle Designer forms (AKA XML forms) can't be merged like normal PDF files. They can only be edited using LCD.

They are using Adobe Acrobat