OVERVIEW
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. It can also be used as a general PDF copying/cropping/re-sizing/OCR-ing manipulation tool. It can generate native or bitmapped PDF output, with an optional OCR layer. There are downloads for MS Windows, Mac OSX, and Linux. The MS Windows version has an integrated GUI. K2pdfopt is
open source
.
Note to MS Word users:
Before using k2pdfopt on your PDF file you might want to check my most recommended solution on my
PDF Conversion Tips
page.
Here's a quick example of what k2pdfopt can do (click on the images below to get the PDF files):
IT TURNS THIS . . .
(8.5 x 11 PDF or DJVU file)
Unsolicited comments from k2pdfopt users (refresh the page to change the comments):
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"... thank you very much for creating and making this wonderful tool available ... Keep up the awesome work!"
-- September 7, 2016
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"Recently I found k2pdf to optimize pdfs for viewing on tablets or ereaders. I am mightily impressed and would like to thank you very much for making it available. I am using it regularly."
-- December 7, 2014
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LATEST NEWS
3 Aug 2019
My site (willus.com)
now offers SSL/https connectivity
. Apparently this happened without my being notified, at no charge to me, which is nice. As a result, today I configured my site (and my backup site
willus.org
) to
automatically re-direct http requests to https requests
. Enjoy the added security!
5 Jan 2019
K2pdfopt v2.51a for MS Windows released. Fixes a bug displaying PDF file information in the MS Windows GUI. The download page now shows v2.51a. The MS Windows binaries will show v2.51a, but the Linux and OSX binaries will show v2.51 since they are not affected by the bug. See details in the
k2pdfopt version history
.
4 Jan 2019
K2pdfopt v2.51
released. This fixes an issue in v2.50 where the Tesseract OCR would not run on modern PCs and enhances the accuracy of the Tesseract v4.0.0 OCR. See details in the
k2pdfopt version history
.
31 Dec 2018
I've posted some k2pdfopt beta Windows builds (link since removed) due to reports of v2.50 Tesseract OCR failing on machines with AVX-capable CPUs (which includes most modern CPUs since Sandybridge). If some people could give me feedback on whether the beta version Tesseract OCR works on their AVX-capable CPU, that would be helpful. If you have time, please try all three versions.
27 Dec 2018
K2pdfopt v2.50 released. The major enhancement in this release is compiling in the Tesseract v4.0.0 library. Most other third-party libraries have also been updated to recent releases. See details in the
k2pdfopt version history
.
15 Oct 2017
Added a new video to the
Mac OSX help page
demonstrating how to download and run k2pdfopt in OSX Sierra.
20 May 2017
K2pdfopt v2.42 released. This revision adds bitmap file output (see -o option), dewarping (like ScanTailor, see -dw option), better auto-cropping (-ac option), and Kobo Aura One device dimensions. See details in the
k2pdfopt version history
.
25 Feb 2017
K2pdfopt v2.41 released. This is mostly a library update, with one minor new feature (erosion filter to thicken text). See details in the
k2pdfopt version history
.
1 Jan 2017
K2pdfopt v2.40 released. Tesseract OCR processing is now multi-threaded and so runs significantly faster on modern, multi-threaded CPUs like Intel's Core-i7. See details in the
k2pdfopt version history
.
26 Nov 2016
K2pdfopt v2.36 released. This is a mostly bug-fix release with some minor new features. See details in the
k2pdfopt version history
.
29 Oct 2016
Added SHA-256 hash code links to the
download page
. You can hover over the buttons or click the "sha-256" links below them.
22 Oct 2016
K2pdfopt v2.35 released. This is a mostly bug-fix release with some minor new features and updated libraries and compiling platforms. See details in the
k2pdfopt version history
.
10 Oct 2016
For now, if you want to run k2pdfopt in Mac OSX Sierra, you'll need versions that are not compressed with UPX, which is
broken in Sierra
. (22 Oct 2016 -- You can now get v2.35 which works in Sierra.)
21 Mar 2016
K2pdfopt v2.34b released. This release fixes
two more MS Windows bugs
. The Linux and Mac versions are not affected (still v2.34a).
[... more news]
ABOUT K2PDFOPT (MORE DETAIL)
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 (Mac/Linux users please see the
mac install notes
or
linux install notes
). 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). Click
Convert All Files
(MS Windows GUI) or 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). You can also drop a folder full of PDF/DJVU files onto the k2pdfopt icon to batch process them. 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 (page ordering will be alphabetical by file name).
See my
k2pdfopt help page
for more detailed help.
Note that some older e-readers (e.g. the first-gen kindle) cannot read PDF files. If you have a Kindle 2, it must have the latest firmware that allows it to
view native PDF files
.
MORE EXAMPLES
(click on images to get PDF file)
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Example Type
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Original
File
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Default Conversion
optimized for 6-inch
screen at 167 dpi
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Smartphone Conversion
(
-odpi 250
)
optimized for 4-inch
screen at 250 dpi
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Text re-flow
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K2PDFOPT
REVIEWS
/
BLOGS
/
FORUMS
/
TWEETS
OTHER PDF/CONVERTING SOFTWARE
See my page on
PDF Conversion Tips
.
RECOMMENDED WINDOWS PDF/E-BOOK READER: SUMATRA
This is my plug for
Krzysztof Kowalczyk's
Sumatra PDF reader
: 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), EPUB, and MOBI. It is a refreshing alternative to Adobe's bloatware. I highly recommend it.
