The visible page is only part of the file.
A PDF can contain text, images, links, form fields and annotations. Drawing a rectangle over a line can change what the page looks like without removing the text object underneath. The behavior depends on the tool and the way the file is saved.
Markup and redaction are different operations.
A drawing or highlight tool is intended to add something to a page. A dedicated redaction tool is intended to remove selected content from the output. If you use a PDF editor, choose its redaction function and follow its export instructions; an opaque shape alone is not evidence that the underlying text was removed.
RedactRoom rebuilds the page images.
The clean PDF is rebuilt from the covered page images. Searchable text, links, forms and accessibility structure are not preserved. This gives the output a different structure from the original document. It is a deliberate trade-off, and it may not fit work that needs selectable text or accessible document structure.
Inspect the exported PDF.
Open the copy you plan to send, rather than relying on the editor's preview. Review each page and the areas you intended to cover.
Try selecting and searching.
If covered text can still be selected, searched or copied, the visible box has not removed that text. An unsuccessful search alone does not prove that every sensitive detail was removed.
Check the surrounding information.
Look for repeated values, page headers, side notes and other context you did not intend to share.
Choose a different tool when the output requires it.
If the redacted PDF must stay searchable or retain document accessibility structure, use a tool that supports those requirements.
Read the checks with their limits.
RedactRoom can provide an export receipt with check results and coverage. This receipt describes export checks. Detection can miss sensitive details. The receipt doesn't confirm that a file was saved or shared.