Even with an increased timeout value it still may not be enough. It will depend on the size of the file and the bandwidth of your connection to the enterprise server.
If you have FTP running on your enterprise server then ftp over to your printqueue and manually FTP the file/member associated with your 800 page PDF. The name of this file would include the job number. The amount of time it takes to FTP in this way would be about the same as what the OneWorld client would need. If your JDENet timeout is lower than this amount then you will not be able to download the PDF through the OneWorld client.
You can theoretically set the JDENet as high as you want. However it can have negative side effects. If the client loses connectivity to the enterprise server the requests sent to that server (bsfn requests, security requests, submit job requests, etc.) will wait up to the timeout before informing the user. This can be frustrating for the user. I have had sites that decided to configure 1800 or 3600 seconds. They produced many massive PDF's per day and decided that it was worth the potential side effects to be able to download via the OneWorld client.
Personally my preferred approach is similar to Carlos'. I use various scripted approached depending on platform to move the files to a network share where the users can get at them. I also will used Optio/Formscape/CreateForm to route these big reports when one of those products is available.
Regards,