SUMMARY
I add several annotations to a pdf document. Then I convert the pdf document to svg with cairo. But as soon as a single text highlighting annotation is added, the conversion breaks.

STEPS TO REPRODUCE
1. Choose a single page pdf document with text and add for example a green text highlight annotation.
2. Save the file as test.pdf
3. convert the file to svg with `pdftocairo -origpagesizes -svg 'test.pdf' vector.svg`
4. Confirm the broken usability of vector.svg

OBSERVED RESULT
All annotations (text, polygon, freehand, image, note) are properly handled by pdftocairo, except text highlight break the conversion

EXPECTED RESULT
All basic annotations should work, especially text highlighting.