Why is some text in PDF to SVG output uppercase/lowercase?

Q:

I have tested yor PDF to SVG product (pdftron.PDF.Convert.ToSvg()) and
it looks really interesting to use as a possible solution. However, in
some pages the demo turns some letters into Uppercase.
I read in the FAQ that the demo takes away some letter, which I
understand. But why does the program turn some letter in uppercases?
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A: It is possible that the PDF has a corrupt ToUnicode Cmap. As a
workaround, disable Unicode mapping as part of PDF to SVG conversion
options (e.g. '--nounicode' in CLI). Assuming that you are embedding
SVG fonts, this will accurately preserve text (provided that your
browser supports SVG fonts – which is sometimes not the case) .