public class AddTextImageSignatureWithParamToPDF {
    
    String API_KEY = '********************************';    
    string DestinationFile = 'AddTxtImageSignWithParameter';    
    string endPointUrl = 'https://api.pdf.co/v1/pdf/edit/add';   
    
    public void addTextImageSignatureToPdf()
    {
        try
        {
            // 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 jsonBody = '{ "async": false, "encrypt": false, "inline": true, "name": "f1040-form-filled", "url": "bytescout-com.s3-us-west-2.amazonaws.com/files/demo-files/cloud-api/pdf-form/f1040.pdf", "annotationsString": "250;20;0-;PDF form filled with PDF.co API;24+bold+italic+underline+strikeout;Arial;FF0000;www.pdf.co;true", "imagesString": "100;180;0-;bytescout-com.s3-us-west-2.amazonaws.com/files/demo-files/cloud-api/pdf-edit/logo.png|400;180;0-;bytescout-com.s3-us-west-2.amazonaws.com/files/demo-files/cloud-api/pdf-edit/logo.png;www.pdf.co;200;200", "fieldsString": "1;topmostSubform[0].Page1[0].f1_02[0];John A. Doe|1;topmostSubform[0].Page1[0].FilingStatus[0].c1_01[1];true|1;topmostSubform[0].Page1[0].YourSocial_ReadOrderControl[0].f1_04[0];123456789" }';

            // Create HTTP client instance
            Http http = new Http();
            HttpRequest request = new HttpRequest();            
            request.setHeader('x-api-key', API_KEY);
            request.setEndpoint(endPointUrl);            
            request.setHeader('Content-Type', 'application/json');
            request.setMethod('POST');            
            request.setBody(jsonBody);            
            HttpResponse response =  http.send(request);
            // Parse JSON response
            Map<String, Object> json = (Map<String, Object>)JSON.deserializeUntyped(response.getBody());            
            if(response.getStatusCode() == 200) 
            {
                if ((Boolean)json.get('error') == false)
                {
                    System.debug('response.getBody() :: '+response.getBody());
                    // Get URL of generated PDF file
                    String resultFileUrl =(String)json.get('url');
                    // Download generated PDF file
                    downloadFile(resultFileUrl, DestinationFile);
                    System.debug('Generated PDF file saved as \'{0}\' file.'+ DestinationFile);
                }
            }
            else
            {
                System.debug('Error Response ' + response.getBody());
                System.Debug(' Status ' + response.getStatus());
                System.Debug(' Status Code' + response.getStatusCode());
                System.Debug(' Response String' + response.toString());
            }
        }
        catch(Exception ex)
        {
            String errorBody = 'Message: ' + ex.getMessage() + ' -- Cause: ' + ex.getCause() + ' -- Stacktrace: ' + ex.getStackTraceString();
            System.Debug(errorBody);
        }
    }
    
    @TestVisible
    private static void downloadFile(String extFileUrl, String DestinationFile)
    {
        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('Error Response ' + res.getBody());
            System.Debug(' Status ' + res.getStatus());
            System.Debug(' Status Code' + res.getStatusCode());
            System.Debug(' Response String' + res.toString());
        }
    }
}

@isTest
private class AddTextImageSignatureWithParamToPDFTest {

    private testmethod static void testAddTxtImgSignToPdf()
    {
        Test.setMock(HttpCalloutMock.class, new AddTextImageSignatureWithParamToPDFTest.AddTxtSignMock());
        Test.startTest();
        AddTextImageSignatureWithParamToPDF addSign = new AddTextImageSignatureWithParamToPDF();
        addSign.addTextImageSignatureToPdf();
        Test.stopTest();
        List<ContentVersion> cv = [select Id, VersionData from ContentVersion];
        System.assertEquals(1, cv.size());
        //String strt1 = cv[0].VersionData.toString();
        //System.assert(strt1.contains('John A. Doe'));
    }
    
    private testmethod static void testAddTxtImgSignToPdfForException()
    {
        Test.startTest();
        AddTextImageSignatureWithParamToPDF addSign = new AddTextImageSignatureWithParamToPDF();
        addSign.addTextImageSignatureToPdf();
        Test.stopTest();        
    }
    
    public class AddTxtSignMock implements HttpCalloutMock {
        public HTTPResponse respond(HTTPRequest req) {
            HttpResponse res = new HttpResponse();
            String testBody = '{ "url": "https://pdf-temp-files.s3.amazonaws.com/03c5c55183c74f8d94a4ec952e4e32ad/f1040-form-filled.pdf", "pageCount": 3, "error": false, "status": 200, "name": "f1040-form-filled", "remainingCredits": 60822 } ';
            res.setHeader('Content-Type', 'application/json');
            res.setBody(testBody);
            res.setStatusCode(200);
            return res;
        }
    }
}