OSError and other problems
Problem 1
1.pdf
not able to function on the pdf with handwritings, only got the blank pics.

Problem 2
2.pdf
It's working on the pdf without handwritings, but there're oserrors when use a different format rather the original one.

I will try to reproduce the issue on my side, thank you for providing the pdf files. What version of pdf2image are you using?

I was unable to reproduce your issue on my side for both PDF using a testing environment that had only pdf2image==1.11.0 and pillow==7.0.0 installed.
First pdf came out with the drawings intact:

Second pdf also came out fine:

What is the installed poppler version on your system? You could be missing a library if it is a more exotic distro (not Ubuntu).