Insane RAM usage by preview.app

Sounds like a corrupt/malformed PDF.

It could have an image that compresses well but grows to an unmanageble size. for example a 1,000,000 x 1,000,000 pixel image of a blank paper could compress to almost nothing (even with lossless compression) but expand to an image that is impossible to display.

I faced the same issue with a perticular pdf and memory usage was insane when I try todo a simple search.

I checked with another pdf with preview app and it was normal and used only few MBs. Then I used a third party app to open the problematic pdf and did the same search as I did with preview app. To my surprise, no abnormal memory usage was observed and the third party app handles the pdf well.

So this only happened with this 28MB particular pdf with preview app. Preview app works well with other pdf files and the problematic pdf works with other third party apps.

I do not what is going on.

Does the "5th" PDF open normally by itself?

It surely does seem like there is a problem with the specific pdf file.

You could try opening it with other applications to see if that makes a difference.

It happens only for a specific pdf for me. I opened it using a third-party app "Skim". And the same thing happened to that app. Previewing as a gallery on Finder doesn't trigger this