Issue Description
When publishing layouts to PDF, Archicad creates separate PDF files for each layout instead of merging them into a single multi‑page PDF document.
Solution
To create one file that contains all PDFs, you will need to create a Publisher Set.
Start by opening the Project Organizer.
The Project Organizer will show an extended view of the Navigator.
1: Select the Publisher icon on the right-hand panel to open up the Publisher Set
2: Select the "+" icon to create a new folder, name the folder.
3: Double-click the folder to open
4: From the lists of layouts on the left, drag the layouts you want as PDFs to the right.
Now you have a list of individual PDF items in the Publisher Set.
5: Select the new folder icon to create a subfolder and drag the PDFs into this new folder. Keep the new folder selected and check the box "Merge into one PDF"
6: Publish the set as usual.