[Sidnicious]

A PDF doesn’t represent a responsive/resizable version of the page so it will look awkward on most screen sizes even if the original would have handled it.

A PDF doesn’t capture scrolling behavior, so a nested scrolling element will lose most of its content, and a page with a chat prompt or cookie notice might have part of its content covered.

A PDF won’t capture even simple interactive elements like image carousels, lightboxes, and collapsible sections, so content may be lost (“oops, I saved it on the second slide of the image carousel, but I really wanted the first one”).

As far as I know, a PDF won’t include embedded audio/video.

Many PDF exporters chunk the document into paper-sized pages (but, to be fair, some don’t).

Not sure if this tool nails all of those cases, but those are reasons why I’ve saved local copies of pages in the past.