The PDF format is meant to be non-editable, but if you scan a document that comes out too light or receive a contract with type that is too faint to read, you need a way to darken a PDF. Here are a ...

Gimp is normally used to create or manipulate images files, but can also work with PDFs if you understand how it works and what it's limits are. If you’ve never used Gimp—a free image editor available ...