According to the UiPath documentation, Page Units are the measure used to license Document Understanding products. Page Units are charged based on the number of pages processed by the Document Understanding models, such as extractors, OCR engines, and classifiers. Therefore, applying OCR on a 10-page document consumes Page Units, while the other options do not. The creation of a Document Validation Action in Action Center does not consume any Page Units, as it is a human-in-the-loop activity. Using ML Classifier on a 21- page document does not consume Page Units, as it is a free model. Using Intelligent Form Extractor on a 5- page document with 0 successful extractions does not consume Page Units, as the extractor only charges for successful extractions.
References:
* AI Center - AI Units
* Document Understanding - Metering & Charging Logic