decompressing lzw stream in pdf file

[mwooding@thecity.sfsu.edu (Miguel Wooding SF Ten.Union)]

I have a pdf file that I can't decipher.  Almost all of the content is
contained within an LZWDecode filter.  The pdf file starts like this:

%PDF-1.2 
{garbage line}
 
11 0 obj
<<
/Length 12 0 R
/Filter /LZWDecode 
>>
stream

{followed by lots of 8-bit garbage, and then:}

endstream
endobj
12 0 obj
4297
endobj
4 0 obj

Is there a tool to decode this and give me a more comprehensible pdf
file? I'd then like to be able to edit the result.

Is there a good place to find out more about pdf files? A primer? A
good dfsg free pdf editor?

Thanks,
--Miguel