adobe acrobat: added

wiki/adobe_acrobat.md

@@ -0,0 +1,15 @@
+# Adobe Acrobat 
+
+[Adobe Acrobat](https://get.adobe.com/reader/) is a PDF reader developed and distributed by
+[Adobe](https://www.adobe.com/).
+It is free.
+
+## Usage
+
+This section addresses the usage of Adobe Acrobat.
+
+### Adding Digital Signatures
+
+In many office applications digital signatures are used that verify a user using a smart card.
+To digitally sign first select `All tools` and `Use a certificate`.
+Then select `Digitally sign` and follow further on-screen instruction.