Are you talking about the page margins? And are you working in normal mode or “Distraction Free” ( )?
In “Distraction Free” mode, the header and footer margins are suppressed from the view to make the flow of text more streamlined. This can make it look like there are no page margins:
If you look in the normal mode, you can see the text is not so close to the page edges:
The view in “Distraction Free” cannot be changed and will always appear without the top and bottom page margins.
If you are looking to change the margins, they are set in the “Layout” dialogue (Document / Page Layout). All margins - top, bottom, left, right, header and footer can be changed here:
The gray lines bordering the text are there to show the outer text margins.
These are turned off/on under View / Show Invisible Elements. You can choose which elements are displayed (and change the display color) under Options / Preferences / Element Display:
If this isn’t what you’re asking, please send a screenshot to illustrate what it is you want to change