Why forcing everything onto A4 looks wrong
Most converters put every image on an A4 page regardless of its shape. A phone photo is 4:3, a screenshot is 16:9, a scanned receipt is long and narrow — none of them are A4, so each arrives floating in a field of white.
That matters when the PDF is being submitted somewhere or read on a phone, where the wasted space is most of the screen.
“Fit each image” gives every page the image's own dimensions, so the document is all content. Choose a paper size only when it genuinely has to be printed or submitted to something expecting one.