Generate and retrieve a presigned URL for accessing a document file by its ID. The URL is valid for a limited time (e.g., 1 hour) and allows secure access to the document stored on DocuPipe. outputFormat options: 'original' (default) — returns the main file stored on DocuPipe. For documents that were converted during upload (HTML, Word, TIFF, WebP, XFA), this returns the converted version (PDF/PNG). 'pdf' — same as original, but for image documents it additionally converts the image to PDF. 'uploaded' — returns the actual file that was originally uploaded, before any conversion. Falls back to 'original' behavior for older documents or documents where no conversion occurred.