You want to share one item from an invoice while keeping the customer number and other details private. Drawing a black rectangle over the text may look convincing while leaving the underlying content in the file. A recipient might still be able to select it, search for it, or recover it from another component. Use an actual redaction feature and treat the resulting copy as a separate document that requires review.
Decide what must be removed
Work on a copy and list the information to remove. Do not focus only on the prominent number on the first page. Names, contact details, and internal notes may appear in headers, attachments, comments, or repeated footers. In a scan, both the visible image and the OCR text layer may matter.
Consider whether the remaining material reveals the same information indirectly. Removing a name achieves little if a nearby personal email address identifies the person. Decide what needs to remain based on the specific reason for sharing. A question about a price usually requires less information than a complete internal review.
Mark, apply, and sanitize
A redaction workflow often separates marking areas from applying the removal. Before applying it, check that every intended area is marked and that necessary content has not been included accidentally. Placing a mark alone does not finish the job. Exact command names vary by application and version.
Use the available sanitization or hidden-information removal options when appropriate. These may concern metadata, comments, or other content that is not immediately visible on the page. Read the options so that useful features are not silently removed. Save the sanitized output with a clearly different name and keep the original separate.
Do not casually upload a confidential document to an arbitrary free website. Establish where processing happens and whether that disclosure is acceptable. A tool that offers drawing or highlighting has not, by that fact alone, demonstrated that it can perform reliable redaction.
Reopen the copy you will share
Reopen the saved output and search for several removed terms. Try copying text from the redacted areas and their surroundings. Inspect document properties, comments, and any attachments. These are useful checks, but they are not an exhaustive security assessment of every possible PDF structure.
For particularly sensitive material, use a second reviewer or the appropriate release process. Send only the reviewed copy, not the editable source or a folder containing both versions. The filename itself may disclose private information, so include it in the final inspection.