Add updf reference (#1072)

README.md

@@ -212,6 +212,7 @@ Any comments, suggestions? [Let us know!](https://github.com/jaywcjlove/awesome-
 * [Spillo](https://bananafishsoftware.com/products/spillo/) - Powerful, beautiful and amazingly fast Pinboard client for OS X.
 * [Tad](https://www.tadviewer.com) - Application for viewing and analyzing tabular data such as CSV files. [![Open-Source Software][OSS Icon]](https://github.com/antonycourtney/tad) ![Freeware][Freeware Icon]
 * [texpad](https://www.texpad.com/) - Great LaTeX editor for Mac with auto-update PDF and autocomplete LaTeX commands.
+* [UPDF](https://updf.com/) - Free PDF editor that makes it possible to read, annotate and edit PDFs, change text and images on Mac. ![Freeware][Freeware Icon] [![App Store][app-store Icon]](https://apps.apple.com/app/id1619925971)
 
 ## Developer Tools