If we look closely, we will see that each and every bar is an exact multiple of the minimum bar width. In a PDF417 symbol , you will always see 1X, 2X, 3X, 4X, 5X, 6X, 7X, or 8X bars. Keep this in mind, you will see later how to detect, and avoid printing problems related to this topic. Like other barcodes, PDF417 has a well defined physical structure. This section describes each of these structural components.
Every bar code has a start pattern on the left, and a stop pattern on the right.
These patterns are unique for each type of bar code. Data is actually stored in codewords. A codeword is a consecutive sequence of 4 bars and 4 spaces totaling 17X wide. The 417 in PDF417 refers to this codeword structure. Codewords reside between the start pattern on the left, and the stop pattern on the right.