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I have a signature application using Pdfbox. When I add a signature, then some text, and then add another signature, the first signature becomes invalid. How can I allow one client to fill in input fields and checkboxes and sign, and then another client can add text and checkboxes and sign the document without invalidating the first signature?

rahim soufiane
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    After the first signer signed the pdf, only a very few kinds of changes are allowed, see [this answer](https://stackoverflow.com/a/16711745/1729265). Thus, you cannot *add text and checkboxes* without breaking the former signature. – mkl May 02 '23 at 22:13
  • unrelated, but 3.0.0-rc1 is not the latest of the 3.0 versions – Tilman Hausherr May 03 '23 at 09:08
  • Hi Tikyou mkl and Tilman, I have a few questions regarding PDFBox digital signatures: What is the default type of signature used in the example provided for PDFBox 3.0.0-rc1? Which version of PDFBox should I use for the latest features and improvements? Could you please share a simple code snippet that demonstrates how to fill fields after signing a PDF document without altering the first signature? Thank you in advance for your help. – rahim soufiane May 04 '23 at 08:00
  • The latest 3.0 is 3.0.0-alpha3. The latest 2.0 is 2.0.28, this is best if you're a beginner. Download the source code and search for the `testSaveIncrementalAfterSign` method in the file `TestCreateSignature.java` in the examples subproject. This does just that. The relevant part is to use `saveIncremental` with an object list (the correct choice of the objects is a bit tricky, sadly) – Tilman Hausherr May 04 '23 at 09:49
  • Thank you for your comments.How can I display the list of signatures and changes in Adobe Acrobat Reader in the left panel of signatures? Specifically, I would like the list to be formatted as follows: Signature 1 Fields changed Signature 2 Is this possible, and if so, how can I achieve this? – rahim soufiane May 04 '23 at 15:32
  • I can't help you about Adobe Reader. Re PDFBox it is possible to display the signatures (see the `ShowSignature.java` example and adjust the output to your needs), but not what was changed. – Tilman Hausherr May 04 '23 at 15:51
  • To clarify, I am wondering whether it is possible to add fields to a PDF document after the first signature has been applied, or if I can only modify the values of existing fields after the first signature. – rahim soufiane May 04 '23 at 16:28
  • Sorry, your text was clear. No you can't add fields, I just tried it. Adobe will complain. mkl also mentioned in his first comment. – Tilman Hausherr May 04 '23 at 17:27
  • tankyou, can i use a variety of fonts apart from Helvetica and can i applying text properties such as bold, italics, and underlining – rahim soufiane May 05 '23 at 15:10
  • Is this a new question? Anyway, just try it. It worked for me but I signed only once and Adobe noticed that the content and properties had changed. The example `CreateSimpleFormWithEmbeddedFont.java` shows how to set a font to a field. Btw "bold, italics, and underlining" isn't a property. You have to choose a font that is bold or italic. Underlining isn't available as a font, you'd have to implement underlining yourself. – Tilman Hausherr May 05 '23 at 17:36

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