We’ve reproduced this issue on our side. GroupDocs.Viewer does not support rendering QR-code fields. We have created a new ticket with ID VIEWERNET-3681 in our bug tracker to investigate this feature. We’ll notify you here in case of any updates.
If you compare it with output from word, the “small” normal sized barcode has 104 pixels, while the 200% “big” QR code has 208 pixels -> 200% the size.
The GroupDocs output of the “big” 200% barcode is pretty close to that with 197 pixels, but the “small” QR code with 100% size is only 57 pixels and not 98 or 99 pixels.
Maybe this will be fixed with the other reported issue anyway, I just want to make sure you are aware of it.