// Create a new annotation and make it invisible
PDAnnotationLink txtLink = new PDAnnotationLink();
txtLink.setInvisible(true);

// Add an action
PDActionURI action = new PDActionURI();
action.setURI(url);
txtLink.setAction(action);

// Create a new rectangle that will be the clickable area
PDRectangle position = new PDRectangle();
position.setLowerLeftX(currentXpos);
position.setLowerLeftY(currentYpos - rectangleHeight);
position.setUpperRightX(currentXpos + rectangleWidth);
position.setUpperRightY(currentYpos);

 // Write the "Link" string in blue
contentStream.setNonStrokingColor(Color.blue);
contentStream.showText(elm.text());
contentStream.setNonStrokingColor(Color.black);

// Make the rectangle a clickable link and add it to the page
txtLink.setRectangle(position);
page.getAnnotations().add(txtLink);