One of PDF417's primary features is error detection and error correction. Each label has 2 codewords of error detection. The error correction capacity may be selected by the user, based on application needs, when the label is to be generated.
Error detection requires two error-detection codewords per symbol.
At the time of printing a PDF417 bar code, the user specifies a security level in the range 0 - 8. In addition to correcting for missing or destroyed data, PDF417 also can recover from misdecodes of codewords. Since it requires two codewords to recover from a misdecode, one to detect the error and one to correct for it, a given security level can support half the number of misdecodes that it can of undecoded codewords. The minimum level of error correction level should be as defined in Table E.1. Higher levels of error correction should be used where significant symbol damage or degradation is anticipated.