Do you need to change the PDF you have on your site? Perhaps a new version of the file is available. Zoomforth allows you to do this without going to the editor and republishing your site. This is especially helpful if the PDF is used on multiple sites since you only have to update the file in the Media Library for all those sites.
All you have to do is select the PDF from the Media Library, then click the "Update PDF" button on the lower right editing panel to select the new version of the file from your computer.