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Willus.com's K2pdfopt
(now with OCR and native PDF output options!)
K2pdfopt optimizes PDF/DJVU files for mobile e-readers (e.g. the Kindle) and smartphones. It works well on multi-column PDF/DJVU files and can re-flow text even on scanned PDF files. K2pdfopt is open source.
Last updated Apr 24, 2013
 

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v1.65
6 Apr 2013

Download
(Windows, Linux, OSX, ARM)

Contrib
(GUIs; Native Kindle PDF Viewer)

Help
(with videos)

FAQ

Forum

History

Source


Linux Install

Mac Install
TURNS THIS . . .

(8.5 x 11 PDF or DJVU file)
   . . . INTO THIS.

(6-inch reader screen)
     . . . OR THIS.

(4-inch smartphone screen)


 
Unsolicited comments from k2pdfopt users (refresh the page to change the comments):

         "Thanks for developing K2pdfopt. A program that can reformat pdfs of SCANNED books, without OCR and text reflow and the associated headache, is a huge blessing. My kindle library has become much more useful." -- March 6, 2012         

         "Thanks so much for your extremely useful software." -- May 2, 2012         

LATEST NEWS
11 Apr 2013    Jens Wallauer continues to update his Windows k2pdfopt GUI, which now supports Tesseract OCR with version 1.04.
6 Apr 2013    K2pdfopt v1.65 released. This is a bug fix / maintenance release with some minor new features. See details in k2pdfopt version history.
12 Jan 2013    Adrian Zandberg's reFlower GUI for k2pdfopt now includes a Windows version. See my k2pdfopt contributions page.
5 Jan 2013    K2pdfopt v1.64a released. This version fixes a native PDF output bug in v1.64. See details in k2pdfopt version history.
4 Jan 2013    K2pdfopt v1.64 released. This version improves the native PDF output so that contents from multiple source pages can reliably be displayed on one output page. It also has some other minor new features and a memory-leak bug fix. See all the v1.64 changes in the k2pdfopt version history.
3 Jan 2013    An OSX GUI for k2pdfopt, reFlower, has been contributed. See my k2pdfopt contributions page. Thanks to Adrian Zandberg.
20 Dec 2012    K2pdfopt v1.63 released. The most notable new feature is Unicode-16 copy/paste support for more languages when using the Tesseract OCR engine. See my OCR help page. See all the v1.63 changes in the k2pdfopt version history.
15 Nov 2012    K2pdfopt v1.62 released. This release is mostly for the KindlePDFViewer team (mobileread.com forum) in that I have significantly re-organized the source code to be easier to integrate with their application. The bulk of the k2pdfopt-specific source code now resides in a k2pdfopt library, and I have eliminated all global variables. There are some minor new features and bug fixes. See the full details in the k2pdfopt version history.
[... more news]


ABOUT K2PDFOPT
K2pdfopt (Kindle 2 PDF Optimizer) is a stand-alone program which optimizes the format of PDF (or DJVU) files for viewing on small (e.g. 6-inch) mobile reader and smartphone screens such as the Kindle's. The output from k2pdfopt is a new (optimized) PDF file. K2pdfopt is meant for text-based files on a white background which may also have graphics or figures, and it works equally well on native and/or scanned or bitmapped PDF or DJVU files. It is fully automated and can batch-process PDF/DJVU files. K2pdfopt works by converting each page of the PDF/DJVU file to a bitmap and then scanning the bitmap for viewable areas (rectangular regions) and cutting and cropping these regions and assembling them into multiple smaller pages without excess margins so that the viewing region is maximized. Making use of this method, k2pdfopt can re-flow text lines, even on scanned documents (see the Winnie the Pooh example below). You can see another example of how k2pdfopt works on this help page.

As of v1.50, k2pdfopt will also embed OCR text into the PDF so that text can be searched and highlighted, and v1.60 can create output files with the native PDF instructions from the source file (if the source file is PDF). Any kind of PDF/DJVU file (best if it has a primarily white background) can be converted. K2pdfopt works especially well on two-column or multi-column PDF/DJVU files such as IEEE and other technical journal articles (see examples below--it auto-detects two-column regions on the page), but even single-column files will often be significantly improved and much easier to read (see examples). K2pdfopt has the advantage over other PDF converters in that it fully preserves the rendered PDF fonts and graphics from the original file, unlike programs that convert the PDF to an e-book format. Also, because k2pdfopt is completely independent of language or fonts, it will work equally well on documents in any language.


HOW TO USE K2PDFOPT
   No install is required and no extra files or packages are necessary to run k2pdfopt. Just drag and drop your PDF/DJVU file icon onto the k2pdfopt icon to convert it. You will be prompted for conversion options (as of v1.16). Press <Enter> to convert the file using the default settings. A new PDF file with _k2opt at the end of the name will be created. The output file is optimized for viewing on Kindles and other mobile readers with 6-inch screens (if the settings are not customized). Or drop a folder full of PDF/DJVU files onto the k2pdfopt icon to batch process. You can even drop a folder full of bitmap images to have them converted into a single PDF as if they were pages of a PDF file.

See my k2pdfopt help page for more detailed help.

Note that if you have a Kindle 2, it must have the latest firmware that allows it to view native PDF files.

EXAMPLES
Example Type Original
File
Optimized
for Kindle

(default settings)
Optimized
for Smartphone

(-odpi 250)
Four-column:
(must use -col 4
See v1.27 changes)

(must use -col 4
See v1.27 changes)
Two-column #2: X X X
One-column X X X
Scanned pages

K2PDFOPT REVIEWS/BLOGS/FORUMS
    1-28-13    Intelligent Rumblings
    1-7-13    Net Buffalo (In Japanese)
    12-1-12    blog.trufanov.com (In Russian)
    11-4-12    abstractmodem.com
    9-20-12    ozgurlukicin.org (in Turkish)
    6-27-12    equiscentrico.com (in Spanish)
    6-26-12    ketabkhan.info (in Persian)
    1-4-12    TechLogon.com
    12-6-11    Herouxapps.com
    12-2-11    note1day.com (in Chinese)
    11-9-11    Świat Czytników (in Polish)
    11-5-11    tivasyk.info (in Ukrainian)
    11-1-11    WMLCloud.com
    10-31-11    linospapa.blogspot.com (in Greek)
    10-27-11    Steve Gibson's Security Now #324
    10-21-11    addictivetips.com
    10-12-11    Paper4Kindle (in Chinese)
    10-7-11    mexxbooks.com (in German)
    10-7-11    the-ebook.org forums (In Russian)
    (varies)    mobileread.com forums
    9-7-11    habrahabr.ru (in Russian)
   
    8-5-11    reddit.com/r/kindle
    8-4-11    steepbend.ru (in Russian)
    8-3-11    ssnjara.wordpress.com (in Croatian)
    8-3-11    xenicom.org (in Italian)
    8-2-11    howtogeek.com (note comments from "willus")
    7-30-11    artiss.co.uk
    7-30-11    ideasfor.info (in Russian)
    7-29-11    vyazovoi.blogspot.com (in Russian)
    7-27-11    guidingtech.com (note comments from "willus")
    7-27-11    tinhte.vn (in Vietnamese)
    7-23-11    triple-click.net (in Greek)
    7-23-11    computerbooks.moole.ru (in Russian)
    7-22-11    blog.rgub.ru (in Russian)
    7-22-11    aldus2006.typepad.fr (in French)
    7-22-11    korben.info (in French)
    7-21-11    expertoeninternet.com (in Spanish)
    7-21-11    eboocek.cz (in Czech)
    7-21-11    lifehacker.ru (in Russian)
    7-20-11    redferret.net
    7-19-11    freewaregenius.com (full review)

OTHER PDF/CONVERTING SOFTWARE
If you're not getting what you want out of k2pdfopt, other utilities may be useful as alternatives to or in conjunction with k2pdfopt, but be sure to "check under the hood" of k2pdfopt--it has many options that make it useful as a generic tool to manipulate PDF files (see my k2pdfopt help pages). Similar utilities to k2pdfopt are PaperCrop (review here), PDFRead, Cut2Col (converts 2-column PDFs to 1-column using an intuitive GUI, written in Java), and SoPDF (open-source PDF-to-Sony reader app written in C++, command-line based). Cut2Col, SoPDF, and, PaperCrop (as of v0.51) all add cropping directives to the PDF file so that all of the original contents are still in the PDF file (in text form and searchable if they started that way)--they are just custom cropped on each new page. K2pdfopt now has this same native PDF output option as of v1.60. Jpdftweak is an excellent "swiss army knife" for PDF files that I use to extract or merge pages from different PDF files. Or try running k2pdfopt with the -mode copy option to optimize scanned PDFs or convert DJVU files to PDF. Briss and PDF Scissors are open-source PDF cropping apps. Calibre is a free, professional mobi-book organizer and converter. PdfMasher is a PDF text-to-mobi converter that claims to be smarter than calibre (or at least to give the user more control over the conversion). The Big List of Free Kindle Tools was posted by freewaregenius.com on 8-28-11.

RECOMMENDED PDF READER: SUMATRA (Windows only)
Some people are surprised to learn that Adobe Reader is not the only choice for viewing PDFs on their PC. I've tried Adobe and Foxit, but I prefer open source, and Krzysztof Kowalczyk's Sumatra PDF reader is a small, efficient, yet feature-rich open-source PDF reader that does everything I want. Sumatra also displays several file types other than PDF, including XPS, DJVU, CBZ, CBR, and PS/EPS (PS/EPS requires Ghostscript). It is a refreshing alternative to Adobe's bloatware. I highly recommend it.

This page last modified
Wednesday, 24-Apr-2013 22:52:55 CDT