My experience with filling in PDF forms using Python. Talk given at SyDjango 2018

1. PDF FORMS
YOONG KANG LIM
SYDJANGO
MARCH 2018

2. WE NEED YOUR APP TO
FILL IN A PDF FORM
”
“

3. CONTEXT
• Inherited Django + Cordova mobile app
• Mobile app sends data to Django app
• Invoice generated in PDF format

4. CONSTRAINTS
• Mobile app used once every sales cycle
• Invoices look totally different each sales cycle
• Client of client signs off on the invoice, we’re not allowed to change
how it looks
• Can’t standardise… customise every sales cycle

5. (NOT
ACTUALLY
THE
FORM)

6. WE WANT
THIS

7. IDEA #1:
LIBREOFFICE

8. LIBREOFFICE
• Programmatically interact with LibreOffice using Python via UNO
(unotools, PyUNO, etc)
• LibreOffice can create PDFs
• Sounds promising…

9. LIBREOFFICE
• Step 1: Convert the form into an image, and make that the
background of ODT document
• Step 2: Put in named fields and/or tables.
• Step 3: Use UNO and unotools to fill them in. For checkboxes,
somehow just put in a unicode check character into the right
field/table cell
• Step 4: Convert to PDF

10. PROBLEMS
• Generated invoice is in lower quality (compression) — client won’t
be happy
• Getting anything to align properly on LibreOffice is impossible
• Super annoying to do… we have 12 different invoices
• Heaps of problems getting UNO to work on later versions of
LibreOffice

12. IDEA #1.5
HTML-TO-PDF

13. PROBLEMS
• Couldn’t find a way to make the HTML/CSS/Fonts/etc look like the
invoice.
• Would have been nice otherwise
• Could also consider RML/ReportLab

14. IDEA #2
FDF

15. WHAT’S FDF?
• “Forms Data Format”
• Worst Wikipedia description ever:

16. FDF
• Basically, you can merge an FDF with a PDF form to get a filled-in
PDF form
• Libraries like fdfgen (https://github.com/ccnmtl/fdfgen) allow you to
generate FDF files from a Python dict
• You can use something called PDFtk to do the merging

17. PDFTK

18. PYPDFTK
• Tried out a library called PyPDFtk
(https://github.com/revolunet/pypdftk)
• It was great!
• Successfully filled in text fields
• Successfully selected radio buttons
• Successfully checked checkboxes
• ….Oh that’s right, we need a signature. Wait, image fields don’t
work!

20. IMAGES IN PDF
• It’s possible.
• Convert an image into PDF, making sure it’s positioned
appropriately
• Merge two pdfs together
• Luckily, I don’t have to implement this myself.

21. PDFJINJA

22. PUT JINJA2 VARIABLES IN TOOLTIP
ADOBE ACROBAT PRO DC

23. SIGNATURE WORKS!
PDFJINJA

24. CHECKBOXES/RADIO BUTTONS DON’T
PDFJINJA

26. PDFJINJA
• So, I had to fork PDFJinja

27. PDFJINJA

28. IT WORKED!

29. DEMO

30. WEIRD STUFF
• Remember PDFtk?
(https://stackoverflow.com/questions/23948647/font-issue-with-
pdftk)

31. FIX
WEIRD STUFF

32. SOME HELPFUL LINKS
THANKS!
• https://github.com/yoongkang/pdffun
• http://rammie.github.io/pdfjinja/
• https://www.pdflabs.com/tools/pdftk-server/
• https://github.com/revolunet/pypdftk