Hi!
It's been more than one and half years since Lupurus's original post - and this has still not been fixed. I'm using Publisher 1.10.5 on Mac OS Monterey (12.6). As seen in the attached screenshots, I'm exporting a single object - a black box - which is exactly 100 x 100 mm. The document is exactly 100 x 100 mm at 300 dpi, no bleed. Using one of Publisher's default export settings - PDF (for print) - the resulting PDF (300 dpi) is exactly 100 x 100 mm but the black box isn't- it has shrunk by one pixel to the right and at the bottom respectively. If I mount the PDF in a new 100 x 100 mm document, the box keeps shrinking - so know my original box is missing 2 pixels to the right and at the bottom. I'm attaching a screenshot of the fourth generation of the box and it's pretty clear what's happening. If I would repeat this scheme a couple of hundred times or so the box will have disappeared. I have also tested rasterizing the PDF in Affinity Photo where 100 x 100 mm (300 dpi) equals 1182 x 1182 px. If I crop off the empty right and bottom edges the remaining black area will only measure 1181 x 1181 px. Case proved that one pixel to the right and at the bottom were not being included in the PDF.
This might seem like a neglectable error but, as pointed out by other posters, can (most probably will) cause complaints from serious printers where this will give preflight warnings etc. It's also highly annoying when mounting the PDF as a PDF passthrough.
THIS IS A BUG AND IT NEEDS TO BE FIXED!