public class ImagesToPDF {
    static String API_KEY = '***********************************';
    static String DestinationFileName = 'result';
    
    public static void addImageToPDF()
    {
        Map<string, Object> parameters = new Map<string, Object>();
        parameters.put('name', DestinationFileName);

        // You can also upload your own file into PDF.co and use it as url. Check "Upload File" samples for code snippets: https://github.com/bytescout/pdf-co-api-samples/tree/master/File%20Upload/    
        String SourceFileUrl = 'https://bytescout-com.s3.amazonaws.com/files/demo-files/cloud-api/image-to-pdf/image1.png,https://bytescout-com.s3.amazonaws.com/files/demo-files/cloud-api/image-to-pdf/image2.jpg';
        parameters.put('url', SourceFileUrl);
        
        string jsonPayload = Json.serialize(parameters);
        System.debug('jsonPayload = '+jsonPayload);
        try
        {
            string url = 'https://api.pdf.co/v1/pdf/convert/from/image';
            HttpRequest req = new HttpRequest();
            req.setBody(jsonPayload);
            req.setHeader('x-api-key', API_KEY);
            req.setHeader('Content-Type', 'application/json');
            req.setEndpoint(url);
            req.setMethod('POST');
            req.setTimeout(60000);
            Http http = new Http();
            HTTPResponse res = http.send(req);
            if(res.getStatusCode() == 200) 
            {
                System.Debug('res ' + res);
                Map<String, Object> deserializedBody =  (Map<String, Object>)JSON.deserializeUntyped(res.getBody());
                String urlVal = (String)deserializedBody.get('url');
                downloadPDFAndStore(urlVal, DestinationFileName);
            }
            else
            {
                System.debug('Success Response ' + res.getBody());
                System.Debug(' Status ' + res.getStatus());
                System.Debug(' Status Code ' + res.getStatusCode());
                System.Debug(' Status String ' + res.toString());
            }
            
        }
        catch(Exception ex)
        {
            String errorBody = 'Message: ' + ex.getMessage() + ' -- Cause: ' + ex.getCause() + ' -- Stacktrace: ' + ex.getStackTraceString();
            System.Debug(errorBody);
        }
    }
    
    @TestVisible
    private static void downloadPDFAndStore(String extFileUrl, String DestinationFile)
    {
        try
        {
            Http h = new Http(); 
            HttpRequest req = new HttpRequest(); 
            extFileUrl = extFileUrl.replace(' ', '%20'); 
            req.setEndpoint(extFileUrl); 
            req.setMethod('GET'); 
            req.setHeader('Content-Type', 'application/pdf'); 
            req.setCompressed(true); 
            req.setTimeout(60000); 
            //Now Send HTTP Request
            HttpResponse res  = h.send(req); 
            if(res.getStatusCode() == 200) 
            {
                blob fileContent = res.getBodyAsBlob();
                ContentVersion conVer = new ContentVersion();
                conVer.ContentLocation = 'S'; // to use S specify this document is in Salesforce, to use E for external files
                conVer.PathOnClient = DestinationFile + '.pdf'; // The files name, extension is very important here which will help the file in preview.
                conVer.Title = DestinationFile; // Display name of the files
                conVer.VersionData = fileContent;
                insert conVer;
                System.Debug('Success');
            }
            else
            {
                System.debug('Success Response ' + res.getBody());
                System.Debug(' Status ' + res.getStatus());
                System.Debug(' Status Code' + res.getStatusCode());
                System.Debug(' Status String' + res.toString());
            }
        }
        catch(Exception ex)
        {
            String errorBody = 'Message: ' + ex.getMessage() + ' -- Cause: ' + ex.getCause() + ' -- Stacktrace: ' + ex.getStackTraceString();
            System.Debug(errorBody);
        }
    }
}

@isTest
private class ImagesToPDFTest {
    private static testMethod void testaddImageToPDF(){
        Test.setMock(HttpCalloutMock.class, new ImagesToPDFMock());
        Test.startTest();
        ImagesToPDF.addImageToPDF();
        Test.stopTest();
    }
    
    private static testMethod void testaddImageToPDFForCatch(){
        Test.startTest();
        ImagesToPDF.addImageToPDF();
        Test.stopTest();
    }
    
    private static testMethod void testaddImageToPDFForDownloadMehtod(){
        Test.setMock(HttpCalloutMock.class, new ImagesToPDFMock());
        Test.startTest();
        ImagesToPDF.downloadPDFAndStore('https://api.pdf.co/v1/pdf/convert/from/image', 'result');
        Test.stopTest();
    }
    
    public class ImagesToPDFMock implements HttpCalloutMock {
        public HTTPResponse respond(HTTPRequest req) {
            HttpResponse res = new HttpResponse();
            res.setHeader('Content-Type', 'application/json');
            res.setBody('{"example":"test"}');
            res.setStatusCode(200);
            return res;
        }
    }
}