Added iOS app and made some minor grammar edits (#138)

* Added iOS app and made some minor grammar edits

* Add PGPro logo picture

docs/_pages/docs/01-best-practices/01-PGP-guide.md

@@ -15,14 +15,26 @@ Learn how to use OpenKeychain to cipher sensible data during RoboSats trade.
 
 Since RoboSats works over the TOR network all communication is end-to-end encrypted. This helps prevents data in transit from being read or tampered by man-in-the-middle attacks. Also, the TOR protocol ensures that the user is connected to the domain name in the browser address bar, in this case the official RoboSats tor address(robosats6tkf3eva7x2voqso3a5wcorsnw34jveyxfqi2fu7oyheasid.onion). However, in RoboSats v0.1.0 the data is transferred as plain text through the front-end and the back-end of the application. This behavior allows the possibility that sensitive data exchanged regarding fiat payment information could be captured by a malicious sniffer on either party's computer or even on the RoboSats server at application abstraction layer. This would represent an attack to the privacy of the owner of the data. Even if RoboSats chat was completely encrypted at every step, you should still not trust that the sensitive data is encrypted. The best practice to avoid this problem is to use asymmetric encryption during the exchange of sensitive data, this guide shows a method that guarantees sensible data confidentiality using the PGP standard.
 
-## OpenKeychain app.
+## PGP Apps
 
-OpenKeychain is an open source Android app that allows to create and manage cryptographic key pairs and sign or/and encrypt/decrypt text and files. OpenKeychain is based on the well established OpenPGP standard making encryption compatible across devices and systems. For a list of compatible software for Windows, Mac OS, and other operating systems check [openpgp.org/software/](https://openpgp.org/software/). Since the concept is the same, this method can be replicated using any another application. OpenKeychain app can be found at F-droid.org [[Link]](https://f-droid.org/packages/org.sufficientlysecure.keychain/) or at Google play store [[Link]](https://play.google.com/store/apps/details?id=org.sufficientlysecure.keychain)
+### Android
+OpenKeychain is an open source Android app that allows you to create and manage cryptographic key pairs and sign or/and encrypt/decrypt text and files. OpenKeychain is based on the well established OpenPGP standard making encryption compatible across devices and systems.  OpenKeychain app can be found at F-droid.org [[Link]](https://f-droid.org/packages/org.sufficientlysecure.keychain/) or at Google play store [[Link]](https://play.google.com/store/apps/details?id=org.sufficientlysecure.keychain).
 
 <div align="center">
     <img src="/assets/images/sensitive-data-PGP-guide/OpenKeychain-logo.png" width="150"/>
 </div>
 
+### iOS
+PGPro is an open source iOS app that allows you to create and manage cryptographic key pairs and sign or/and encrypt/decrypt text and files. PGPro is based on ObjectivePGP which is compatible with OpenPGP. It can be found on their website [[Link]](https://pgpro.app/) or the Apple App Store [[Link]](https://apps.apple.com/us/app/pgpro/id1481696997).
+
+<div align="center">
+    <img src="/assets/images/sensitive-data-PGP-guide/PGPro-logo.png" width="150"/>
+</div>
+
+### Other
+For a list of compatible software for Windows, Mac OS, and other operating systems check [openpgp.org/software/](https://openpgp.org/software/). Since the concept is the same, this method can be replicated using any another application.
+
+
 ## Encryption schema.
 
 In most cases, the sensitive information we would want to protect is the seller's fiat payment information, i.e. phone number, PayPal account, etc. So, the image below shows the encryption scheme that ensures that the seller payment information can only be read by the buyer.