In order to leverage as much as possible Oracle BPM out-of-the box functionalities, I decided to add this document as a readonly attachment. We can easily achieve this operation within Worklist Application, but it is a bit more challenging when we want to attach the document during the Human Task initialization. 

After some investigations (on BPM 11g PS4FP and PS5), here's the way to go:

1. Create an asynchronous BPM process, and use this xsd to create 2 Business Objects FullPayload and PartialPayload :

2. Create 2 process variables 'vFullPayload' and 'vPartialPayload' using this Business Objects created above

3. Implement the Start Event with the initial Data Association, with an input argument using 'FullPayload' Business Object type

4. Drag in an User Task into the process. Implement the User Task as usual by using 'vPartialPayload' type as the input type and assign the task to your favorite tester (mine is jcooper)

5. Here's the main course - Start the Data Association and map the payload into 'execData' as follow:

FROM	TO
vFullPayload.attachment.mimetype	execData.attachment[1].mimeType
vFullPayload.attachment.filename	execData.attachment[1].name
bpmn:getDataObject('vFullPayload')/ns:attachment/ns:content	execData.attachment[1].content
'BPM'	execData.attachment[1].attachmentScope
false()	execData.attachment[1].doesBelongToParent
'weblogic'	execData.attachment[1].updateBy
xp20:current-dateTime()	execData.attachment[1].updateDate

(Note: Check the <Humantask>WorkflowTask.xsd file in your project xsd folder to discover the different options for attachmentScope & storageType)

6. Your process is completed. Just build a standard ADF UI and deploy the process/UI onto your BPM Server for the testing. Here's an example, with a base64 encoded pdf file: application-pdf.txt

7. Finally, go to the BPM Worklist application to check the result !

Please note that Oracle BPM, by default, limits the attachment document size to 2Mb. If you are planning to have bigger attachments in your process, it is recommended to store your documents in a Content Management server (such as Oracle UCM) and pass the reference instead. It is possible to configure Oracle BPM to store attachment directly into Oracle UCM too, and I believe we can use the storageType, ucmMetadataItem attributes for this purpose.... I will confirm once I have access onto an Oracle UCM for the testing :)