This is the same in AC12 (2156), using Publisher (not Plotmaker).
Pubished PDF files get significantly smaller (sometimes half or less) if you turn off transparency of placed .tif images.
AC is not an image editor, and thus needs to export all the components into the PDF file, placing the burden on the output unit (i. e. the printer). Files grow, and some printers choke.
So the advice remains: If possible, overlay, crop and edit bitmapped images in a photo editor (like Photoshop) before dragging them into Archicad.
AC4.1-AC26SWE; MacOS13.5.1; MP5,1+MBP16,1