I have to connect several PDFs I've authored together in free tools. For example, one PDF could be a compiled LyX document and another could be scanned result.

I'm looking for a free tool that would easily allow me to do that.


  • Free to use (bonus points for open source).
  • Simple to use, and to show other people to use.
  • Command line is fine, but UI is nicer.
  • Has to run on windows.
  • Has to be really straightforward to use.
  • Has to produce valid PDF files.

Preferably standalone.

  • For Linux, I would be able to provide you with a concat *.pdf kind of script which uses gs. If gs is available for Windows, this might help you.
    – Bernhard
    Commented Feb 25, 2014 at 6:39
  • @Bernhard GS is available for Windows, but there are probably better options. For Linux you wouldn't even need the script to remember the crazy flags for using GS, tools like pdfunite just take a list of file names as arguments (the last one being the output file).
    – Caleb
    Commented Feb 25, 2014 at 8:06

3 Answers 3


This is a pretty common task and will be covered by a lot of different software packages. Which one is best for you is going to depend more on what else you want done that on just a merge function.

  • The most widely known candidate is probably PDFtk, the PDF Tool Kit from PDF labs. The command line portion in open source and will do what you need quite easily.

    The command line usage to combine two files (in order) into a merged single one would go something like this:

    pdftk.exe file1.pdf file2.pdf cat output merged.pdf
    • There is even a free (as in beer) GUI front end for Windows. Of course the GUI would allow you to select files, order the output and create the merged file through a point and click interface.

      PDFtk free GUI

      While the backend is GPL'ed, the company that produces that is trying to make a buck on the side by dual licencing it to include in commercial software and the GUI part is not open-source at all.

    • There is however and independent project called pdftk4all that uses the open-source portion of the backend and provides an alternative open source front end. The UI isn't quite as polished bit it looks like it will do the job.

      pdftk4all GUI

    • As if that wasn't enough, PDFTK Builder is another OSS front end to PDFtk. I'll spare you the screen shot as it's much the same as the previous entry, but the last activity on the project was 2009 (as opposed to 2013 for pdftk4all above), so this probably isn't the thing to grab.

  • Another promising option in the spirit of open-source is PDFsam. The basic version is free in all senses and the enhanced version with encryption and a few fancy plugins is donation-ware. The procedure for merging files using the GUI looks remarkably versatile, even allowing partial page ranges of the source files to be used.

    PDFsam basic GUI

  • Honorable mention in the command-line-only department needs to be made for Ghost Script. The reason this might be worth considering over the PDFtk command line option above (which is simpler) is that you can also handle other media types. Post Script and even raw image files can be processed and merged into PDF output.

    gswin32c.exe -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile=merged.pdf file1.pdf file2.pdf file3.ps

There are quite a number of alternatives in this space that I am not familiar with. You might find one in that list that is better suited to your other needs beyond basic merging. For good measure if you need a quick hack, there are also a number of free tools that will do this online without having to install any software at all. See MergePDF or PDF Cloud for two.


PDFArchitect/PDFCreator: two for the price of one.

  • Free to use (bonus points for open source): Mainly - Free for basic operations, PDF Architect has some extra editing features that aren't free. Also Open Source
  • Simple to use, and to show other people to use" Very; PDFCreator: just file->print (from pretty much any Windows program) PDFArchitect->open pdf file(s)->drag and drop pages/cut and paste.
  • Command line is fine, but UI is nicer: UI
  • Has to run on windows: Designed for it
  • Has to be really straightforward to use: Very.
  • Has to produce valid PDF files: As far as I know; haven't run them through any actual testing processes but visually and openable by any program I've thrown them at.

I found this very simple GUI here. My first tests showed that

  • I could us it on both Linux and Windows
  • It did not install and change register of Windows.
  • It meet the requirement of attaching PDF documents from different sources such as open office, google docs, adobe, and scanned files.
  • It's very small in size.
  • It does not ask you to buy anything else or upgrade or popping.
  • It can attach large files and large number of files.
  • It can resize files such that different standards of documents attach uniformly.

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