I’d suggested Adobe Reader previously as you’d not mentioned success with that tool, and I’d suggested verifying the format of the doc using a so-called “preflight” tool (“preflight” tools are how PDF files are verified), and you’ll want to try that.
And you’ll want to send links to this thread and to the problem PDF doc to the Apple feedback link.
The three groups that can potentially fix this rendering are the folks that created the document (NCERT) if there are different and more compatible document-generating or copy-protection settings that can be employed, the folks supporting the document-producing tool, and the folks at Apple that support the PDF rendering and/or the error messages when some part mis-renders and/or is otherwise unsupported; if the doc can be re-made more compatible with the Apple reader, or if the doc created is out of spec, or if the doc is in spec and mis-rendered or mis-diagnostic’d.
PDF documents (usually) follow a standard, though there are incompatible extensions with differing support by different renderers, and there are buggy PDF generation tools, and yes, buggy PDF viewers, and PDF viewers that do not support some of the extensions. Without access to that doc—which is pretty clearly under a restrictive copyright—nobody here in the forums can determine what specific case is arising here, and only the folks mentioned previously can fix this.
If you’re interested in learning more about PDF files, start here: https://en.wikipedia.org/wiki/PDF/A
