To fix faded or missing lines on my printed documents, there are a few steps I should follow:

1. Check the ink level in the printer.
2. Clean the printer heads.
3. Install new ink cartridges.
4. Make sure the margins are set correctly.
5. Check the paper quality for any damaged/aged materials.
6. Check the software settings to make sure the correct settings are enabled for the document.

Taking these steps should help identify and fix any faded or missing lines from my printed documents.