This superimposes one document on another so both print together. It is how a plain content file gets combined with a letterhead or a pre-printed form without either being redesigned.
Merging puts pages one after another. Overlaying puts them on top of each other.
The overlay typically repeats or stops. Check the output.
Where it is opaque, yes. Use a transparent PNG or a faint watermark instead if that is a problem.
These tools handle one document at a time. When the job is thousands of files, Greenbooks handles document digitization as a managed service, including bulk scanning, OCR and metadata capture, with the output loaded into DocuVenta DMS. Talk to us about volume work.