If during a document upload the document is in the conversion queue a long time (longer than 5 minutes for a single A4 text document) there may be an error with the conversion process.
When a document is uploaded, the Skyline server renames it to an internal unique file name and marks the status as “Queued”. The Skyline website does not convert an uploaded document to PDF. This is controlled by three services called "Skyline PDF Scheduler”, "Skyline PDF Converter" and "DCStart". If any one of these services are not running or one of the settings used by the services has changed then the document will be stuck in the status "Queued".
The most likely cause is that one of the services is not running or that an uploaded document has jammed the PDF conversion. Follow the instructions on how to clear uploaded documents.