low resolution pdf export on Mac

Hi, wondering if anyone else using Office 365 on Mac has this same problem.

I'm trying to export/print some Excel charts to a pdf file, using Apple's built-in pdf writer (aside from an expensive ongoing Adobe Acrobat subscription this appears to be the only way to do this).

The resolution of vector image (the dots and lines on my charts) looks horrible! If I export the same thing from a PC (using the built-in Microsoft print-to-pdf function), they look perfect - left side on the attached image is the Mac export / right from a PC. 

In a bit of research, it seems like this might have been a problem with vector images from Office on Mac (for example, PowerPoint) for a long time, so was hoping there might be a work-around?

I tried using the Adobe online convertor (https://www.adobe.com/nz/acrobat/online/excel-to-pdf.html?promoid=Z662FSMK&mv=other) which produces clear chart images...but it also replaces fonts, doesn't calculate formulas properly, and gives you no control over what worksheets it uses.   

Thanks in advance!