To add the entire page in PageSnip just navigate to the web page you want, right-click the mouse and select the Add Page option:
PageSnip will download the HTML page and then process it just like it would any other selection.
Note: Sometimes the page will not display 100% like it appears on the web.
This is usually because there are server side interactions between the web page and the browser that alter the appearance of the page with Javascript. PageSnip makes every effort to obtain all the CSS files, images and even external Javascript files so that the assembly of a full snipped page will look just like it does on the web. But since the paths to the images and files changes with the saved content - this is not always possible.
The good news is that most pages will render correctly and PageSnip is constantly being tweaked to improve the display of the content you gather.