How can I convert a long pdf document to pages

If the document source that produced the PDF is available and is a Word document or Rich Text (RTF), consider opening it directly in Pages, or using LibreOffice 24.2.4 to open and then export it to Word. That would be the least headache approach.

PDF is an end-stage formatted document designed for viewing or printing. Its internal organization is organized far differently than it appears visually and that structure is forboding for document conversion. At least document conversion that does not result in huge time consumption cleaning up the resulting document. Many offer PDF to Word or PDF to Pages conversion tools — online and offline — and these should come with a caveat emptor regarding the preceding sentence.

That said, you can open that PDF in Adobe Acrobat Pro, another PDF Editor (not Apple's Preview) that supports PDF to Word conversion, or Microsoft Word v16.31 or later to convert it to a Word DOCX document that can in turn, be opened in Pages.

I happen to have Office 2021 for Mac installed and its Word v16.86 does a passable job of converting PDFs (including those with equations) into Word DOCX documents. It is not perfect and one should proofread the resulting document and tidy up some words or spelling. If you don't have Word or Adobe Acrobat Pro, consider using someone else's to at least get your Word document output.

It looks like you can directly open your Word document using Pages, or copy all the content from Word into Pages. This should be the simplest method. Converting from PDF to Pages may potentially have formatting issues.

You are welcome.