Although there isn't a direct feature to create borders on Google Docs, there are 3 workarounds that you can use to create that appearance.

With tables in Docs, you can insert an image in one cell and the caption in the cell beneath it. If you want to make a gallery, increase the columns and rows and add more images with captions.

Lucky for you, adding page numbers to your digital documents, whether that's a technical manual on Google Docs or an eBook on Microsoft Word, is a pretty straightforward process.