visibility attribute

Type:"visible" or "hidden"
Used By:input, All block elements

The visibility attribute can be set to "hidden" to prevent block from appearing on the page. Although useful in HTML for dynamic effects, most of the time in pdf this simply causes the block to not be drawn (although space is still allocated for it on the page, unlike when the display attribute is set to "none").

The exception to this is with form fields, created by the input tag. These can be placed on the page but set to invisible, and can then be made visible at a later date by the use of JavaScript.

Creates two form fields. The first is invisible, but is made visible when the second one is clicked on.

<INPUT type="text" name="popup" value="This text was hidden" visibility="true"/>
<INPUT type="button" onClick="pdf:show(popup)" value="Show Popup"/>