Tooltips in PDFs: are they possible?

I'm using the tc开发者_Python百科pdf PHP class for creating PDFs. Is there any solution to add tooltips to links?

Links itself cannot have tooltips. Viewers always show the URL.

But TCPDF can add "Annotations", which is the closest you can get to tooltips (but have to be assigned to a rectangle area instead of to text/paragraphs). http://www.tecnick.com/pagefiles/tcpdf/doc/com-tecnick-tcpdf/TCPDF.html#methodAnnotation

You'll have to refer to the PDF specification. Section 8.4 and 8.4.5, and you are looking for "Popup". http://www.adobe.com/devnet/pdf/pdfs/PDFReference16.pdf

I don't think so... seems the library doesn't support it, I even haven't met it in practice.

BTW they are called comments in PDF.