This script allows you to download view-only PDF's on Google Drive. Simply open the document, scroll through it until all pages are loaded and then execute this script in your browser console. This script has some improvements compared to other scripts and avoids blur on high-resolution images.

pdfdownload.js

let pdfScript = document.createElement("script");
function rescale(width, height, fitWidth, fitHeight) {
    let ratio = width / height;
    let fitRatio = fitWidth / fitHeight;
    if (ratio <= fitRatio) {
        // Dimensions to fit are wider, fix the width
        return [width, width / fitRatio];
    } else {
        // Dimensions to fit are taller, fix the height
        return [height * fitRatio, height];
    }
}
function imageToBase64(img) {
    let canvas = document.createElement("canvas");
    let context = canvas.getContext("2d");
    canvas.width = img.naturalWidth;
    canvas.height = img.naturalHeight;
    context.drawImage(img, 0, 0, img.naturalWidth, img.naturalHeight);
    return canvas.toDataURL("image/png", 1.0);
}
pdfScript.onload = function () {
    try {
        let jsPDF = window.jspdf.jsPDF;
        let pdf = new jsPDF();
        let pdfWidth = pdf.internal.pageSize.getWidth();
        let pdfHeight = pdf.internal.pageSize.getHeight();
        let pdfRatio = pdfWidth / pdfHeight;
        let elements = document.getElementsByTagName("img");
        for (let img of elements) {
            if (!/^blob:/.test(img.src)) {
                continue;
            }
            console.log("adding image", img.src);
            let imgData = imageToBase64(img);
            let [newWidth, newHeight] = rescale(pdfWidth, pdfHeight, img.naturalWidth, img.naturalHeight);
            pdf.addImage(imgData, "png", 0, 0, newWidth, newHeight);
            pdf.addPage();
        }
        pdf.deletePage(pdf.internal.getNumberOfPages());
        pdf.save("download.pdf");
    } catch(e) {
        console.log(e);
    }
};
 
pdfScript.src = "https://unpkg.com/jspdf@latest/dist/jspdf.umd.min.js";
document.body.appendChild(pdfScript);

I think this script might be outdated with some new security permissions. You have to add a trusted script url assignment in order for your scripts url to be trusted. Some browsers might not support this struct of trusted script url; however, chrome does and this code I have pasted below is for chrome.

let pdfScript = document.createElement("script");
function rescale(width, height, fitWidth, fitHeight) {
    let ratio = width / height;
    let fitRatio = fitWidth / fitHeight;
    if (ratio <= fitRatio) {
        // Dimensions to fit are wider, fix the width
        return [width, width / fitRatio];
    } else {
        // Dimensions to fit are taller, fix the height
        return [height * fitRatio, height];
    }
}
function imageToBase64(img) {
    let canvas = document.createElement("canvas");
    let context = canvas.getContext("2d");
    canvas.width = img.naturalWidth;
    canvas.height = img.naturalHeight;
    context.drawImage(img, 0, 0, img.naturalWidth, img.naturalHeight);
    return canvas.toDataURL("image/png", 1.0);
}
pdfScript.onload = function () {
    try {
        let jsPDF = window.jspdf.jsPDF;
        let pdf = new jsPDF();
        let pdfWidth = pdf.internal.pageSize.getWidth();
        let pdfHeight = pdf.internal.pageSize.getHeight();
        let pdfRatio = pdfWidth / pdfHeight;
        let elements = document.getElementsByTagName("img");
        for (let img of elements) {
            if (!/^blob:/.test(img.src)) {
                continue;
            }
            console.log("adding image", img.src);
            let imgData = imageToBase64(img);
            let [newWidth, newHeight] = rescale(pdfWidth, pdfHeight, img.naturalWidth, img.naturalHeight);
            pdf.addImage(imgData, "png", 0, 0, newWidth, newHeight);
            pdf.addPage();
        }
        pdf.deletePage(pdf.internal.getNumberOfPages());
        pdf.save("download.pdf");
    } catch(e) {
        console.log(e);
    }
};

const myScriptPolicy = trustedTypes.createPolicy('my-script-policy', {
  createScriptURL: (url) => {
    return url; 
  }
});

const trustedUrl = myScriptPolicy.createScriptURL ('https://unpkg.com/jspdf@latest/dist/jspdf.umd.min.js');
pdfScript.src = trustedUrl;
document.body.appendChild(pdfScript);