In Xerox scanners/photocopiers randomly alter numbers in scanned documents, computer scientist David Kriesel shows that the Xerox WorkCentre 7535 randomly changes the numbers in its scans. The copier has firmware that tries to compress images by recognizing the numbers and letters in the documents it scans, and when it misinterprets those numbers, it produces untrustworthy output. The bug also occurs in the Xerox 7556 and possibly other machines, and as Kriesel points out, this could mean that engineering diagrams, invoices, prescriptions, architectural drawings and other documents whose numeric values are potentially a matter of life-and-death (or at least financial stability) are being randomly edited by machines we count on to produce faithful copies.
Now, let us scan the construction plan and get a PDF file from it. No OCR, just plain image. Then, we get wrong square meter numbers at the three places 8-O (Yeah, couldn't believe it, too). The screen shots of the erroneous places are organized in the below table. There is one additional line in the table for the original patches. The Xerox WorkCentre 7535 always produced the same errors; this is why we only need one line for it in the table. In contrast, the WorkCentre 7556 randomly produced different numbers, this is why I present three lines for three runs with different errors.