This comment links to
I right-click both in Safari, opening new private viewing tabs then click PDF on each page.
The first one (1.) displays fine, but the second one (2.) either draws the page very slowly (tens of seconds) or fails completely. Partially generated text/images disappear if I scroll them off and back on to the screen. It’s a little bit like erasing a white board.
However searching for text shows that it’s there, just not rendered. Below are screenshots of my browser window and then the view of the saved PDF in Preview, searching for instances of “Astro”.
I have seen several PDFs in the past that were somewhat slow (fractions of a second, just long enough to be visually disturbing when trying to skim a document) updating both in Safari and in Preview that I’ve never seen in much older versions of macOS or in Chrome, but I’ve always put off asking about it as it’s been hard to reproduce in a way that can make a good Stack Exchange quesiton.
But here I’ve got a specific document and screen shots.
Question: Why is display of this PDF very slow and ultimately fails in Safari for me?
macOS 10.15.7, Safari 14.0
above: online PDF viewed in Safari, below: saved PDF viewed in Preview.