Download pages as PNG from Apryse's pdftron WebViewer

Apryse_pdftron_webviewer_downloader.js

/*
1.  Click "Digital Textbook"
2.  Open in new tab
3.  Select "Page by page"
5.  Select "Single page"
6.  Select "Fit to page"
7.  Go to page 1
8.  Open Devtools
9.  Use Devtools' Select tool to click on the page.
10. Switch to Devtool's console tab and run the script
11. Using MacOS's Finder, select all downloaded PNGs. To get the pages in the
    right order, you may need to: Sort files by Date Added asc. Select Page 1
    image, shift+click and select last page image file.
12. Right click and use MacOS's "Create PDF" to combine all the PNGs into a
    single PDF.
13. Delete all the PNGs

You may need to allow website to download multiple files
*/

function downloadURI(uri, name) {
	var link = document.createElement("a");
	link.download = name;
	link.href = uri;
	document.body.appendChild(link);
	link.click();
	document.body.removeChild(link);
	delete link;
}

function savePage(pageNumber) {
	const canvas = document.querySelector(`#pageContainer${pageNumber} > canvas.hacc`)
	const dataUrl = canvas.toDataURL("image/png")
	downloadURI(dataUrl, `page${pageNumber}`)
}

async function nextPage() {
	const button = document.querySelector("button[aria-label='Next page']")
	if (button.disabled) {
		// Can't go to next page (at end?)
		return false
	}

	button.click()
	await sleep(200)
	return true
}

function sleep(ms) {
	return new Promise(resolve => setTimeout(resolve, ms));
}

async function run() {
	var page = 1
	do {
		savePage(page++)
	} while (await nextPage());
}

await run()