how to show pdf file in ionic app with out download

You will need to use ng-pdfviewer.

AngularJS PDF viewer directive using pdf.js.

<button ng-click="prevPage()">&lt;</button>
<button ng-click="nextPage()">&gt;</button>
<br>
<span>{{currentPage}}/{{totalPages}}</span>
<br>
<pdfviewer src="https://stackoverflow.com/questions/43496455/test.pdf" on-page-load='pageLoaded(page,total)' id="viewer"></pdfviewer>

and in your AngularJS code:

var app = angular.module('testApp', [ 'ngPDFViewer' ]);

app.controller('TestCtrl', [ '$scope', 'PDFViewerService', function($scope, pdf) {
    $scope.viewer = pdf.Instance("viewer");

    $scope.nextPage = function() {
        $scope.viewer.nextPage();
    };

    $scope.prevPage = function() {
        $scope.viewer.prevPage();
    };

    $scope.pageLoaded = function(curPage, totalPages) {
        $scope.currentPage = curPage;
        $scope.totalPages = totalPages;
    };
}]);