Acrobat's definition of hidden text does not determine whether it is obscured by other objects. Rather it looks for text with a special "invisible" rendering mode (see text rendering mode in 32000-1). This invisible mode is only commonly used in OCR, to provide hidden text for searching in addition to the original image. Using the PDFEdit layer a plug-in may iterate recursively through all text and remove text based on rendering mode. Removing text may affect the position of subsequent text, so the removed text must be replaced by an adjustment to positioning for subsequent elements in the same text group.
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