Update README.md

hwding · web-flow · commit 69109bfcb713 · 2017-08-22T01:39:00.000+08:00
diff --git a/README.md b/README.md
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 # pdf-unstamper
 Text stamp remover for PDF files.
 
+Powered by [Apache PDFBox®](https://pdfbox.apache.org/)
+
 ## Run
 ```
 ➜ java -jar pdf-unstamper.jar [ARGUMENTS]...
