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    <p>In the uncompressed pdf document, there are "stream objects" of following uncertain format ((0,0) being bottom left) in pseudo regexp form:</p> <pre><code>(x1 y1 m x2 y2 l [whitespace or blank or newline seperator symbol])* S (BT .* ET)* </code></pre> <p>where</p> <pre><code>x1, y1, x2, y2 are coordinates l probably for "draw line" m move to, "from to" or "merge" S is the command for "draw" or the like BT Begin Text ET End Text </code></pre> <p>all commands postfix.</p> <p>EDIT:</p> <p>one possible Java regexp is (ref PDF32000_2008.pdf), after replacing newlines by blanks in the uncompressed pdf source: </p> <pre><code>((\s+\d+(\.\d+)?){2}(\s+m|\s+l|(\s+\d+(\.\d+)?){2}(\s+re|\s+y|\s+v|(\s+\d+(\.\d+)?){2}\s+c))\s+)+([SsFn]|[fBb](\*)?) </code></pre> <p>There are other elements like "W*" or "Q q" in the stream which seem to adjust line thickness or font properties at general. Since I was not able to find a language spec ad hoc, this is what I infer from experiments.</p> <p>Using this information and the coordinates of the text tokens (between ET and BT), one can infer table cell widths, table starting end ending positions (for identifying different tables). </p> <p>The problem remains uncompressing streams of any kind. With pdftk I was able to uncompress pdf files created from openoffice writer, but arbitrary pdf files have still cryptic symbols in them.</p> <p>Further information: </p> <p><a href="http://www.gnupdf.org/Introduction_to_PDF" rel="nofollow noreferrer">http://www.gnupdf.org/Introduction_to_PDF</a></p> <p><a href="http://blog.idrsolutions.com/2011/05/understanding-the-pdf-file-format-%E2%80%93-carriage-returns-spaces-and-other-gaps/" rel="nofollow noreferrer">http://blog.idrsolutions.com/2011/05/understanding-the-pdf-file-format-%E2%80%93-carriage-returns-spaces-and-other-gaps/</a></p> <p><a href="http://blog.idrsolutions.com/2012/03/understanding-the-pdf-file-format-names-locations/" rel="nofollow noreferrer">http://blog.idrsolutions.com/2012/03/understanding-the-pdf-file-format-names-locations/</a></p> <p><a href="http://blog.idrsolutions.com/2011/05/understanding-the-pdf-file-format-%E2%80%93-pdf-xref-tables-explained/" rel="nofollow noreferrer">http://blog.idrsolutions.com/2011/05/understanding-the-pdf-file-format-%E2%80%93-pdf-xref-tables-explained/</a></p> <p><a href="https://stackoverflow.com/questions/4150069/pdf-page-stream-optimizer-library">PDF page-stream optimizer library?</a></p> <p><a href="http://www.gnupdf.org/Stream" rel="nofollow noreferrer">http://www.gnupdf.org/Stream</a></p>
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    1. COWhile I appreciate the time you've spent on this answer, it is also incomplete and potentially misleading. If you want to know how a PDF file is laid out, go to http://www.adobe.com/devnet/acrobat.html and download the Acrobat SDK. Part of that is the Adobe PDF file format specification (which is now also an ISO standard, ISO 32.000 to be specific). You'll find the full meaning of all of these pesky PDF operators and how to correctly uncompress PDF streams...
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      1. USDavid van Driessche
    2. COYou mean to say adobe acrobat sdk includes some uncomression tool delivering readable text of stream objects content (more reliable than pdftk's "compress|uncompress" commands)? I would definitely appreciate a hint on this.
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    3. CONot exactly, the SDK contains the PDF file format specification that explains how to perform the uncompression. It also explains how you can use Adobe Acrobat, for example by writing plug-ins, to do many of these tasks. If all you want to do is simply look at the file structure of a PDF file, there are a number of cool tools that can do this. There was (and maybe still is) a product called Browser from Enfocus and there is pdfToolbox from callas (I'm affiliated with this company) that lets you explore the low level structure of a PDF file (including the page streams).
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