TCPDF not render all CSS properties

Supported tags are: a, b, blockquote, br, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, img, li, ol, p, pre, small, span, strong, sub, sup, table, tcpdf, td, th, thead, tr, tt, u, ul

All the HTML attributes must be enclosed in double-quotes

In the first place, you should note that PDF and HTML and different formats that hardly have anything in common. If TCPDF allows you to provide input data using HTML and CSS it's because it implements a simple parser for these two languages and tries to figure out how to translate that into PDF. So it's logical that TCPDF only supports a little subset of the HTML and CSS specification and, even in supported stuff, it's probably not as perfect as in first class web browsers.

Said that, the question is: what's supported and what's not? The documentation basically skips the issue and let's you enjoy the trial and error method.

Having a look at the source code, we can see there's a protected method called TCPDF::getHtmlDomArray() that, among other things, parses CSS declarations. I can see stuff like font-family, list-style-type or text-indent but there's no margin or padding as far as I can see and, definitively, there's no float at all.

To sum up: with TCPDF, you can use CSS for some basic formatting. If you need to convert from HTML to PDF, it's the wrong tool. (If that's the case, may I suggest wkhtmltopdf?)

TCPDF 5.9.010 (2010-10-27) - Support for CSS properties 'border-spacing' and 'padding' for tables were added.