Updating the readme.

Author: user

README.md

@@ -36,9 +36,13 @@ Return the number of pages for a given PDF
 
 ### `replace_page`
 Replace a page in a PDF (pdf_path) by the PDF pointed by pdf_to_insert_path.
- - pdf_path is the PDF that will have its page replaced.
- - page_number is the number of the page in pdf_path to be replaced. It is 1-based.
- - pdf_to_insert_path is the PDF that will be inserted at the old page.
+ - `pdf_path` is the PDF that will have its page replaced.
+ - `page_number` is the number of the page in pdf_path to be replaced. It is 1-based.
+ - `pdf_to_insert_path` is the PDF that will be inserted at the old page.
+ 
+### `stamp`
+Applies a stamp (from `stamp_pdf_path`) to the PDF file in `pdf_path`. Useful for watermark purposes.
+If not `output_pdf_path` is provided, it returns a temporary file with the result PDF.
 
 
 ## Example