I’m trying to show changes to a document that I have revised without having to draw lines manually along the right side of the document
The normal procedure is to record (or track) changes, Edit > Track changes > Record. This gives a quick way for the owner of the document to see, accept or reject changes. Before you do this you need have filled in at least one name field in Tools > Options > LibreOffice > User Data
There is Help on Record changes. Also starting on page 64 of the Writer guide 7.1 (in Documentation) is more on tracking changes
Having pointed you towards the normal procedure we have to address the issue of how to highlight your changes.
- If you received the document through email, you could open a new instance of the document from email and give it a different name, e.g. [filename]v2.ods. You can then turn on track changes and, using your edited copy as a guide, edit the new document. You will see deletions as crossings-out in orange, additions also in orange with your name against the changes. The owner of the document can right click on each change and choose whether to accept or reject.
- If you just want to comment your changes in the document that you already edited, select each changed text, right-click and select Add Comment. Write your note in the box at the side. When you come to print the document you can choose whether to print the comments and where to print them in the LibreOffice Writer tab of the Print dialog.