How to save images in their original quality

[zwo1a]

When I use the scanner's ESCL driver, the scanner seems to return JPEG images and I can clearly see the JPEG compression Artifact.
When I import a JPEG image to NAPS2 via drag and drop and save it again, the image size changes.
The same goes for images in PDF, which can be stored losslessly in PDF format, but NAPS2 doesn't seem to do that.
Is it possible to save this image in this case in its original quality and original encoding without re-encoding.
Thanks.