lopdf is a Rust library for PDF document manipulation. It is used by the printpdf which is relatively popular. lopdf is the vital for safe work with PDF documents without the need to depend on the unsafe libraries like poppler.
For example see how to modify the existing PDF file:
let mut doc = Document::load("example.pdf")?; doc.version = "1.4".to_string(); doc.replace_text(1, "Hello World!", "Modified text!"); doc.save("modified.pdf")?;