Ok. So overcame CSF violations.
Looking at the error logs for the AdobePDFEmbedAPI, I just have lots of these:

Error creating tenant view 'OSUSR_say_Settings_T20' for table 'OSUSR_say_Settings': Invalid object name 'OSUSR_SAY_SETTINGS'.
Cannot find the object 'OSUSR_SAY_SETTINGS_T20', because it does not exist or you do not have permission.
eSpaceVer: Id=0, PubId=0, CompiledWith=11.14.0.33133
RequestUrl: (Method: )
AppDomain: CompilerService.exe
Path: C:\...\PS\
Locale:
DateFormat: yyyy-MM-dd
PID: 4528 ('CompilerService', Started='11/25/2021 5:59:07 PM', Priv=409Mb, Virt=2864Mb)
TID: 210
Thread Name:
.NET: 4.0.30319.42000
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at OutSystems.HubEdition.Extensibility.Data.ExecutionService.BaseExecutionService.ExecuteNonQuery(IDbCommand cmd)
at OutSystems.Internal.Db.Command.ExecuteNonQuery(String description, Boolean isApplication, Boolean skipLog, Boolean applyTransformationsToParameters)
at OutSystems.Server.Services.ApplicationRuntimeOperations.Infrastructure.Repositories.Tenants.TenantUpdateViewsFromSQL.CreateTenantView(Dictionary`2 tableInfos, Int32 tenantId, ObjectKey eSpaceKey, IEnumerable`1 catalogs, Action`2 onCreatingTenantViewForTableError, Dictionary`2& toInsert, Dictionary`2& toUpdate)
I notice that the AdobePDFEmbedAPI only lists these errors for tenant number 20, which is the default tenant, but also largely unused - it's used for demo purposes really.
When I look at the error logs for my module, it looks like this:

I note that these errors exist here for tenant 287 too, which is the tenant that I've been trying to develop the PDF function for.
I've no idea what the errors mean, so I'm not even sure if they're relevant.
Screen still shows same as previous post: RE File preview error.