What is PDF Clown?
PDF Clown is a free/libre and open-source general-purpose Java and .NET library for manipulating PDF files through multiple abstraction layers, rigorously adhering to PDF 1.7 Specification (ISO 32000-1).

If you want to know more, please see the Overview.

Where does the weird name ‘PDF Clown’ come from?
That’s a joking combination of two circumstances: I love clowns (so smiling!) and, in the fanciful world of circus, clowns are companions of acrobats (any reference to existing products is purely accidental! *;o) ).

Smiling might be a major therapy for the world: could people just respect one another, we’d have solved a large portion of current troubles. Around the Web there’s a nice piece of poetry describing smiles:

A smile costs nothing,
but gives much.

It enriches those who receive it,
without impoverishing those who give it.

It takes nothing but a moment,
but the memory of it sometimes lasts forever.

None is so rich or mighty that he can get along without it,
and none is so poor but that he can be made rich by it.

A smile creates happiness in the home,
fosters good will in business,
and is the countersign of friendship.

It brings rest to the weary,
cheer to the discouraged,
sunshine to the sad,
and is nature's best antidote for trouble.

Yet it cannot be bought, begged, borrowed, or stolen,
for it is something that is of no value to anyone until it is given away.

And, if you meet someone who is too weary to give you a smile, leave one of yours.
For no one needs a smile quite so much as he who has none left to give.



PDF Clown is open source software: so I can do whatever I want with it, can’t I?
Gotcha! Yeah, PDF Clown is Open Source Software, a special breed of it in fact: Free Software. But being Free Software or simply Open Source Software doesn’t imply that you have an unlimited right upon it: you can do only what’s prescribed by the applicable license (LGPL, see below). If you don’t agree with this license, you are not allowed to use PDF Clown, neither in binary nor in source form. This license is used especially to protect the product against possible abuses.

PDF Clown is “free” in the sense that its contributors, approving the economical, political and philosophical implications of the FLOSS paradigm, judged beneficial for the community to make it available as a common effort for sharing knowledge, without lucrative bottom lines or oppressive per-user fees.

So if you got any benefit from using PDF Clown, it would be humanly appreciable to honor our gift supporting this project in any of the following mutualistic ways:

  • contributing code to enhance the library;
  • sharing your expertise with other users;
  • donating to the project via PayPal;
  • promoting the use of PDF Clown by putting a link on your site, recommending it to other people on mailing lists and user forums, writing articles about it in magazines, and so on;
  • promoting the general adoption of FLOSS by your company, your local administration and your government.

Thank you!

Can PDF Clown be used by commercial applications?
Yep! It suffices that your company agrees to the LGPL: your commercial applications will keep closed and profitable, but any modification (enhancement or bug-fix) to the PDF Clown’s implementation that you may have applied will have to be made available as open source at no cost.

PDF Clown can be used by your own product as long as you don’t change the copyright notices; you also have to distribute the source code of PDF Clown to your clients (see the next FAQ for further details about its requirements).

So: you can use PDF Clown’s library from your commercial software without hassle (LGPL is your friend), but you can’t inject PDF Clown’s code inside your closed-source commercial software or remove its copyright notices.

To get further information about LGPL, please read the next FAQ.

LGPL sounds confusing to me: could you explain it?
GNU Lesser General Public License (LGPL) is the license applied to the PDF Clown library, which grants users the following rights:

  • freedom to run the program for any purpose
  • freedom to study how the program works, and change it to make it do what you wish
  • freedom to redistribute copies so you can help your neighbor
  • freedom to improve the program, and release your improvements (and modified versions in general) to the public, so that the whole community benefits

Along with the aforementioned GPL freedoms, LGPL specifies an additional provision allowing the library to be linked with non-(L)GPLed programs: this practically implies that you can use PDF Clown with any software, may it be open- (free software) or closed- (proprietary software) source.

Precisely, LGPL distinguishes between works *based* on the library and works which *use* the library:

  • [use] your software can be linked (both statically and dynamically) to the PDF Clown library without distributing your source code;
  • [based] if you make any modification to the PDF Clown library, such modified version MUST be distributed along with its source code (including your modifications).

So: your software can *use* the PDF Clown library keeping closed its own code, but if you *adapt* the PDF Clown library, the modified library’s source code MUST be distributed (please note that also in the latter case your software can use the PDF Clown library keeping closed its own code). May you need to keep closed even your adapted PDF Clown library, OEM/ISV licenses are available (see the next FAQ).

When you distribute your program using PDF Clown (either self-hosted or as a service), you have to accomplish some requirements:

  • give notice that your program uses PDF Clown, and that PDF Clown is covered by LGPL (might there be a section of your documentation and/or a dialog box displayed by your program which expose copyright notices, you have to show PDF Clown’s copyright notice as well);
  • supply the PDF Clown library source code, or give notice of the way it can be obtained mentioning its home URL (;
  • supply a copy of the LGPL (you can find it included in the downloadable distribution).
What if we needed to adapt the library’s code base without disclosing it?
As a general-purpose PDF library, PDF Clown can be adapted to disparate use contexts, but PDF Clown’s license (LGPL, see above) requires that any modification you apply to the library’s source code MUST be made freely available to anyone. If you needed an “asymmetrical” license to keep closed your valuable adaptation, OEM/ISV commercial licenses are available — might you be interested, please contact us for a quote, thanks.

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