Error Code Where Convert PDF in PHP with FPDF

Might I ask how you propose we would fix unseen code?
Why not provide the code that generates the above? Surely readers will be in a better position to give you an answer than is currently the case.
I suspect it may be a result of character/character sets used. I also note that your pdf doesn't appear to contain the 'contains binary content' flag, though I can't remember if that was a part of the spec for PDF v1.3, nor can I remember what fPdf's approach is 0 whether it's staticm or adapts to the content - IIRC, a pdf that uses flate compression should signify that it contains binary data (i.e, the file isn't comprised only of the first 128 chars - it uses the full 8bits of each char)

I ended up hating fpdf so much that I rewrote a workable before ported it to C++. (I couldn't work out how to, or indeed if you could add (a) bookmarks (b) file attachments.

In any case, it's a pretty weird output - objects out of order, streams found without attributes. Oi Vey!

Here's a 'binary content included' header:
25 50 44 46 2D 31 2E 34 0A 00 78 30 31 00 78 30 32 00 78 30 34 00 78 30 33 0A

Or in human form (. stands in for non-printable 00 character, ◙ stands in for 0A)
%PDF-1.4◙.x01.x02.x04.x03◙

And an example of a correct stream:
38 20 30 20 6F 62 6A 0A 3C 3C 2F 4C 65 6E 67 74 68 20 34 37 2F 46 69 6C 74 65 72 5B 2F 46 6C 61 74 65 44 65 63 6F 64 65 5D 3E 3E 0A 73 74 72 65 61 6D 0A 48 89 33 34 D0 33 50 30 04 11 B9 5C A6 16 A6 30 4E 0E 57 30 32 17 26 67 61 6C 04 54 81 90 84 F0 73 B9 C0 06 20 24 91 B8 50 39 B0 08 48 1F 00 0A 65 6E 64 73 74 72 65 61 6D 0A 65 6E 64 6F 62 6A 0A

Again, in a form we're more familiar with:
8 0 obj
<</Length 47/Filter[/FlateDecode]>>
stream
H‰34Ð3P0¹\¦¦0NW02&galT„ðs¹À $‘¸P9°H
endstream
endobj