Today, when reading a PDF document with the ipad, I found that every page is too white, the font is very small, it is troublesome to manually zoom in every page of the ibooks. So search to remove the PDF to leave the white method.
First I hope that the Linux system from the Pdfcrop, the results of a variety of options, found that the PDF size has not changed, or the original 8.5x8.9 inch.
Later, search for the use of Ghostscript, the PaperSize or resolution forced to change to the desired value, still no change. Depressed.
Later found a pdfcrop version of the Web, also written in Perl, just a little more friendly, after the attempt still does not work. Use your own hardcode to change the results you want, failure. But the biggest discovery in the tool is 1inch=28.3464567bp (DPI).
A summary of the experience of one night's failure is that the PDF document is scanned for pictures in PDF format, rather than text directly, so tools such as Pdfcrop cannot be found and processed in white.
Finally in the online search PDF Margin crop, accidentally found Briss, holding to try to download the mentality of the use of a moment, found that can recognize the picture into a PDF of the text area, drag the upper left or right side of the Blue Square area can also be a manual selection of reserved areas, terrific.
The use method is to download Briss, decompress, and then execute
Java-jar Briss-0.0.13.jar
or
java-jar briss-0.0.13.jar cropthis.pdf
(the second line comes in handy if you w Ant shortlinks for PDF editing)
For more detailed instructions see Briss:crop your PDF documents using a visual interface.