I solved the issue.
The problem was in a way the data is delivered from the server to the client.
It is critical to assure that the server sends the data in Base64 encoding, otherwise the client side can't deserialize the PDF string back to the binary format. Below, you can find the full solution.

Server-side:

OutputStream pdfStream = PDFGenerator.pdfGenerate(data);



String pdfFileName = test_pdf;



// represent PDF as byteArray for further serialization

byte[] byteArray = ((java.io.ByteArrayOutputStream) pdfStream).toByteArray();



// serialize PDF to Base64

byte[] encodedBytes = java.util.Base64.getEncoder().encode(byteArray);



response.reset();

response.addHeader(Pragma, public);

response.addHeader(Cache-Control, max-age=0);

response.setHeader(Content-disposition, attachment;filename= + pdfFileName);

response.setContentType(application/pdf);



// avoid byte shaving by specifying precise length of transferred data

response.setContentLength(encodedBytes.length);



// send to output stream

ServletOutputStream servletOutputStream = response.getOutputStream();



servletOutputStream.write(encodedBytes);

servletOutputStream.flush();

servletOutputStream.close();

Client side:

let binaryString = window.atob(data);



let binaryLen = binaryString.length;



let bytes = new Uint8Array(binaryLen);



for (let i = 0; i < binaryLen; i++) {

    let ascii = binaryString.charCodeAt(i);

    bytes[i] = ascii;

}



let blob = new Blob([bytes], {type: application/pdf});



let link = document.createElement('a');



link.href = window.URL.createObjectURL(blob);

link.download = pdfFileName;



link.click();

Reference topics:

• How to convert a PDF generating in response.outputStream to a Base64 encoding




• Download File from Bytes in JavaScript