SharePoint 2013: Conversion Job Settings cannot be Changed after Items have been Added to the Job in Word Automation Services

An issue was reported to me where an exception was generated while my admins were trying to use word automation services to convert some word documents in pdf format. They were constantly facing with this exception:

System.InvalidOperationException was unhandled

HResult=-2146233079

Message=Conversion job settings cannot be changed after items have been added

to


the job.

Source=Microsoft.Office.Word.Server

StackTrace:

at Microsoft.Office.Word.Server.Conversions.ConversionJobSettings.

set_OutputFormat(SaveFormat
 value)

at WordAutomationService.Program.

Main(String[]
 args)

in

at System.AppDomain.

_nExecuteAssembly(RuntimeAssembly
 assembly, String[] args)

at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()

at System.Threading.ExecutionContext.

RunInternal(ExecutionContext
 executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)

at System.Threading.ExecutionContext.

Run(ExecutionContext
 executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)

at System.Threading.ExecutionContext.

Run(ExecutionContext
 executionContext, ContextCallback callback, Object state)

at System.Threading.ThreadHelper.ThreadStart()

After reviewing the source code I found the following:

1.cJob.AddLibrary(sourceList, destList);

2.ConversionJobSettings settings = rahulJOb.Settings;

3.settings.OutputFormat = SaveFormat.PDF;

4.cJob.Start();

In the code above it is evident that the job settings were tried to be modified after adding source and destination document libraries. The code was modified and the lines 2 and 3 were moved above the
cJob.AddLibrary(sourceList, destList) and the issue was confirmed to be resolved.