PDF Document Processor prevents PDF from being closed until the Client is closed
When a PDF has been loaded by a PDF Document Processor (on the scanning form or the electronic delivery form), the filesystem keeps a lock on that file until the ILLiad client is closed. This is because the processor is not closing the file.
Angela Mott commented
Example: If the PDFs are scanned into the c:\program files (x86)\illiad\elecdel folder, then when they're imported into the scanning form they cannot be sent out.
Workaround: Save the PDFs into another folder and then they should be able to import and send.