Some customer PDF files have garbage character prepended to the file

[Rob Tow]

Some of our customers are submitting PDF files that have "garbage" characters prepended to the file, such that the Linux "file" utility will nbot recognize the the file as a PDF. I am wondering if this actually has a purpose, such as pre-press job-control. An example of the start of such a PDF file (using the hexeditor GHex to display readable results) :

u\UffffffffZj\Uffffffffe\Uffffffff\u01ad\Uffffffff\Uffffffff\Uffffffff\Uffffffffh\Uffffffffhi\Uffffffff\Uffffffff\UffffffffPDF-1.2

%\Uffffffff\Uffffffff\Uffffffff

1 0 obj

<<

/Author (Pro API)

/CreationDate (D:20211013132107Z)

/ModDate (D:20211013132107Z)

/Creator (PRO HLCAPI)

/Title (PRO Document)

/Producer (CrawfordTech PDF Driver Version 4.2 32 Bit Build ID 5163 on February 29, 2016 at 20:01:07)

/Subject ()

>>

endobj

5 0 obj

<</Length 8764 /Filter /FlateDecode >>

[radzmar]

If you remove \Uffffffff, which might be a undefined character in UTF-32, you getting this.

u\Zjeƭhhi
PDF-1.2

%

1 0 obj

Maybe it's a just kind of signature of the CrawfordTech PDF Driver used for creating this PDF. But I'm just guessing.