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# fileIdentifier

Gets the file identifier for a PDF document.

```
var fileIdentifier: CGPDFArrayRef? { get }
```

## Discussion

A PDF file identifier is defined in the PDF specification as an array of two strings, the first of which is a permanent identifier that doesn’t change even when the file is updated. The second string changes each time the file is updated. For more information, see *PDF Reference: Version 1.3 (Second Edition)*, Adobe Systems Incorporated.

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