1. Use marking and matching functions when editing papers, such as highlighting or underlining with different colors to mark important contents, problems, errors, etc. At this point, these marks will remain when the paper is opened.
2. The reading software used (such as PDF reader) enables the annotation or annotation function by default when opening the paper. These functions will mark the paper with different colors for readers to mark and annotate, but will not affect the content of the paper itself.