Is there a difference between the PDF version exported from ArcGIS Pro 1.4.1 layouts and that produced by ArcGIS Desktop 10.4.1?
I ask because I am seeing PDFs exported from ArcGIS Pro (600dpi) that look perfect in Adobe Acrobat Reader DC but when sent to either of two printers (no others tested) there are some grid lines (from Create Fishnet) that show up about 10 times as thick as they should. The same thing happens in the scale bar and there is bad "blockiness" in two picture elements (logos) on the layout too.
Although the two PDFs are created quite differently (ArcGIS Pro vs ArcMap, using ArcPy in each case to do the same map series) these symptoms are not seen in the ArcMap PDFs but are seen in all such maps from Pro.
The hardcopy is from an A0 HP plotter and an A3 printer so I think the problem is the PDF rather than either plotter/printer.
A mobile phone photo of the hardcopy, although quite blurry, illustrates the symptoms. Note the thick black line on the scale bar at bottom right (the rest is the expected thin lines), the two thick blue lines on the index map at lower left (the rest are the expected thin lines) and two thick grey lines on the grid in the main map (the rest are the expected thin lines).
Curiously, the same layout exported as a TIFF (600dpi) and imported into Adobe Acrobat Pro before being saved as a PDF prints fine from that PDF. However, this is a workaround that is only viable for a subset of requirements because it requires manual creation of the final PDF (in an otherwise automated system), results if TIFF file sizes that are 10x as big and take 10x as long to create, and require licensing of Adobe Acrobat Pro.