NULNUL coming as header

[PDFBeginner]

In our Application we have functionality to view / download PDF files Below is the code used for download and display in browser

> while ((readLength = bufInputStream.read(buf)) != -1) { outStream.write(buf, 0, readLength); } } 

recently we observed like getting popup like "There was an error opening this document. The file is damaged and could not be repaired."

when we checked the contents of good and bad pdf

good.pdf starts with "%PDF-1.6" ends with "%%EOF"

bad.pdf starts with "NULNULNULNUL%PDF-1.6" ends with "some number123456"

When we checked with Original PDF , which was streamed have proper header(without NUL)

We printed byte stream data and its coming as

First 500 bytes of PDF stream = [0, 0, 0, 0, 0, 0, 0, 0, 37, 80, 68, 70, 45, 49, 46, 51, 10, 37, -30, -29

• when NUL NUL header added , why %%EOF Not appended to streamed data?
• is there any setting we can add %%EOF by automatically to streamed data?
• we need to do a code change for this?
• there is any Acrobat or WebSphere  or loadbalancer or browser setting to resolve this issue?

[Test Screen Name]

Not really about Reader. The PDF specification says %PDF must be st the first byte but some software accepts some extra bytes. You can choose to do the same.

%%EOF is required at the end. Nothing should be adding it to a stream. Sounds like your bad PDF is just bad 

[PDFBeginner]

Just want to know from experts on below items

• What all possibilities for these NUL to be added in front of Header?
• All data transmission  in encrypted mode(TLS)
• Host file don't have these NUL characters
• we tried to read data through wireshark , but due to encrpyted , we could not able to identify is it NUL or something else
• Any softwares could help to get transmitted data ?
• Temp fix has been added like add %%EOF at end of the file

[PDFBeginner]

metadata of the file has been changed from host and when download via application, what is possibility in change of metadata?

1.From Host file <x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP Core 4.1.1">

2.From App downloaded same file <x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 5.2-c001 63.143651, 2012/04/05-09:01:49        ">

3.xap tag change to xmp when downloaded as below

file at host

<xap:ModifyDate>2018-05-21T08:35:15-04:00</xap:ModifyDate>

App downloaded same file

<xmp:ModifyDate>2018-05-09T22:15:42-04:00</xmp:ModifyDate>

[Test Screen Name]

I don't know what app or service you are talking about, so it's hard to say where you should find the experts. Clearly this is the wrong forum.