I suggest you learn the basics of CSS and HTML (it's very easy), and you'll know what you can and cannot remove.
Briefly, if the style says a piece of text is "Arial, 14pt, blue, bold", it's fixing the properties, and you generally cannot change them on the fly. Remove the "14pt" part and the size will be the default one, which lets you change it in the reader. It will still be blue and bold.
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