"Before being printed, please pay your attention to the comments that have been made." This is incorrect and people will struggle to understand what you mean. They'll only understand from the preceding context. You should rewrite it as, "Before printing it, please pay attention to the comments that have been made.", or more explicitly, "Before printing your thesis, please pay attention to the comments that have been made.

Your thesis is okay to me given that this is for a diploma level programme. Before being printed, please pay your attention to the comments that have been made. "before being printed" is fine, but not so good in this combination. before being printed is passive, as if the thesis is the subject, yet you follow with an instruction to the person. So maybe better to go in this direction Your thesis is okay to me given that this is for a diploma level programme. Before having it printed, please pay attention to the comments that have been made. "your" is assumed. Your thesis is okay to me given that this is for a diploma level programme. Before going to print, please pay attention to the comments that have been made. Your thesis is okay to me given that this is for a diploma level programme. Before going to print, please attend to the comments that have been made. "okay" is quiite informal.