What happened since you were last able to export Pages content to an acceptable PDF size? Did you add additional large images, tables, or charts to the existing Pages document content? Did you upgrade your version of iPadOS or Pages (e.g. v14.2)?
Pages will ask the operating system to use its PDF creation framework (e.g. Quartz PDFContext) when exporting a Pages document to PDF, and it is not impossible that Apple has munged that PDF Creation framework if the same newsletter now explodes in size. Other than reviewing what new content you may have added to the newsletter, there is little you can do in Pages for iPadOS to reduce the exported PDF file size.