Thanks for your help, but it seems to be the same file as from the link I got it (same size).
The result of running PatchFinder is:
./PatchFinder
###################################################################
===================================================================
Welcome to the ESRI Patch Finder utility
===================================================================
###################################################################
This utility automatically detects which ESRI product is currently
installed on your system. It also detects all currently installed
Service Packs, Hot Fixes and Patches.
At any prompt, press the Return key to accept the default option
shown in parenthesis or press 'q' to quit and exit this utility.
The following products were found on your system.
Select a Product to Search
===================================================================
(1) ArcGIS Web Adaptor for the Java Platform
Please make a selection from the list above or to quit (1): 1
Searching ArcGIS Web Adaptor for the Java Platform ...
*********ArcGIS Web Adaptor (Java Platform) install summary:********
ArcGIS Web Adaptor (Java Platform) 10.3 Install Location:
/opt/arcgis/webadaptor10.3/java
*******************************************************************
Actually I have ArcGIS for Server and WebAdaptor 10.3.1 installed and removed WebAdaptor 10.3.