While a file is read

A file moves through these stages, and the workspace shows each one with its page count as it runs:

1. Virus scan
2. Split and render every page
3. Text recognition (scanned pages only)
4. Document classification: which document each page belongs to
5. Extraction and the forensic checks on every page
6. The cross-document checks, then the red file

How long it takes depends on the number of pages and how busy the readers are. You can leave the page: the file keeps being read, and the red file is waiting when you come back. A page that cannot be read is marked, never skipped silently.