In addition to previous updates that give you more control over formatting in Google Docs, such as viewing non-printing characters and enhancements to content organization, Google are introducing the option to display line numbers within Docs that are set to paged mode.
The numbers are automatically calculated next to each line in the document, and can be configurable for the entire document, a page, or a specific section. Additionally, these numbers are preserved when printing.
This feature makes it easier for you to reference specific content positions in documents, particularly when collaborating with others on long or complex content.
Please click on the link to find out more, Google Workspace Updates: Adding line numbers to Google Docs (googleblog.com)