e-signature

I want to implement the adobe e-signature functionality, it works fine when I am uploading a file from input type file but I need to do this with the relative path of the file. I have search a lot in google but doesn't find any relevant answers. I am using PHP

Please suggest your answers in PHP CURL of AJAX

$("#form").submit(function(e){

  e.preventDefault();

  var path = "<?=$_SERVER['DOCUMENT_ROOT']?>"+"ptaxtool/digitalFile/adobe.pdf";

  var form = new FormData($(this)[0]);

  form.append("File",path);

  var settings = {

  "async": true,

   "crossDomain": true,

   "url": "https://api.na1.echosign.com/api/rest/v5/transientDocuments",

   "method": "POST",

   "headers": {

     "access-token": "<?=$access_token?>"

   },

   "processData": false,

   "contentType": false,

    "mimeType": "multipart/form-data",

    "data": form

  }

  $.ajax(settings).done(function (response) {

   console.log(response);

  });

  })