Mac: How to Blacken PDFs easily and effectively

Mac: How to Blacken PDFs easily and effectively


An embarrassing, sometimes legally fatal error arises when trying to block text with black boxes. […]

The widely used PDF files capture text and images almost exactly as they appear in the application they were created with. The format is designed to store text and both bitmap and vector images, with the text available for searching, copying and even editing in the right application. This part of copying can lead to a sea of problems when people try to remove details from a PDF file before sending it-such as details from a court case, from government documents, or even from corporate communications – by dragging black boxes over the words and paragraphs they want to protect.

However, in most cases, drawing frames over text in a PDF will only add the frames, the text below will not be deleted. Someone who wants to extract the text under the obfuscation can simply drag it over the area with a selection tool or choose the Select all option on the page. The copied text can then be pasted into a word processor or text editor.

These black box overlays have led to embarrassing and legally disastrous situations that date back several decades. Two notable incidents: the accidental release of information in a file in 2011 in a long-running legal battle between Apple and Samsung, and the disclosure of key allegations in the indictment against Paul Manafort in 2019 that concerned his connection to an alleged employee with Russian ties.

If you need to remove text from a document before you send it-and you can’t just eliminate the information in the source document that created the PDF and create a new one-you can resort to multiple apps to snip secret, legally prohibited, embarrassing, or protected text from a PDF before you get it on the go.

macOS Preview App

The preview warns when you try to draw over text, because it doesn’t really remove the text from a PDF file (above). Instead, use the “Blacken” tool, which also explains itself.

Apple has added a editing tool and editing alerts in Preview for macOS Big Sur. You will notice this when you select certain tools in the Preview marker toolbar. Show this toolbar by selecting View > Show Marker Bar, or by clicking the Marker icon on the right side of the default toolbar, just to the left of the search box.

Click on any item in the “Shapes” menu, including a line with the thickness of the sixth or seventh heavy option, and the preview will come up with a warning: the content behind this inscription will not be deleted. She advises you to use the new Black selection tool.


Most tools in shapes (outlined with a red rectangle) provoke a redaction warning because they do not remove text; instead, select the Redact tool (marked with a red arrow).

Choose this tool and you will get another warning: edited content will be permanently removed. Apple further explains: all content marked for blackening will be permanently deleted when the document is closed. (You can check these two warnings so you never see them again).

Drag the Blacken selection tool over the text, and a black bar with an X pattern appears. Back up, and the text cannot be recovered from this version of the file, although you can select a previous version before editing with File > Return to or pull a copy from a Time Machine backup.


The blackening in the preview uses a special pattern. It is permanent when you save the file.

Adobe Acrobat

Adobe Acrobat Pro DC (part of a Creative Cloud subscription) also offers a blackening tool available through Edit & gt; Blacken Text and Images. Adobe will warn you how the feature outstaffing works when you first select it.


Acrobat alerts you that the text will be permanently removed and also offers a cleanup option.

When the tool is selected, you can drag over text and images that Acrobat marks with a red outline to indicate that they will be completely removed when you save the file. Acrobat inserts a new file name with the word “blackening” the next time the file is saved manually to prevent overwriting of the original.

Acrobat also includes a cleanup feature that removes a bunch of hidden metadata, such as the author of the document, which is often prefilled with the name of the person using the computer or app; invisible but searchable layers of text that are created when a document is imported as a bunch of images and the text is algorithmically identified; and any text that goes beyond a page or is entirely in the margins and cannot be selected.


Above: Acrobat displays the text selection for blackening before saving the file. Below: The saved file now shows black bars (without hidden Text).

Cleanup is automatically selected when you apply blackening, although you can flip a switch to disable it. You can perform the cleanup separately without blacking visible text by clicking Clean Document.

PDFpen and PDFpen Pro

Smile’s PDFpen and PDFpen Pro also have a blackening feature. You can either select text via Tools > Select Text, or select a range via Tools > Select Rectangle, and then apply Format & gt; Edit Text – Block. The result is a blackened image.


For PDFpen, you first select the text or region using a standard tool, and then apply blackening using a menu option.

Both versions also offer the Format > Edit – Delete Text function, which removes the text and leaves white areas instead of black areas. This can be advantageous in documents with a white background.

*Glenn Fleishman writes, among other things, for

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