Okular consumes an enormous amount of Memory (it reached over 1Gb today).
I got the same tab list opened (and loaded) over the weeks (even months): it consists of 7 or 8 tabs the size of each is in range 4 to 17 Mb (there’s no large files).
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.87.0
Qt Version: 5.15.2
Kernel Version: 5.14.10-1-MANJARO (64-bit)
Graphics Platform: X11
Processors: 12 × Intel® Core™ i7-8750H CPU @ 2.20GHz
Memory: 15,5 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 1060 with Max-Q Design/PCIe/SSE2
Okular Version 21.08.2