Open your Google Doc
Click Insert
Click Table
Select 1 x 1
Type or paste your content into the table cell
Resize the table if needed
Click inside the table
Use the toolbar to change border color, border width, or border style
To hide the inner look, keep the single cell and adjust the border settings
For a page border, click Insert
Click Drawing
Click New
Add a shape or line border
Save and close the drawing
Position the drawing on the page as needed