The WPS PDF toolkit: merge, split and convert in one place

Merge: PDF tools → Merge, reorder and export;
Split: by page range or every N pages;
Convert: PDF to Office keeps tables and images;
Compress: three quality levels for email limits;
Encrypt: open password plus editing permission.

The built-in PDF toolkit merges, splits, compresses, encrypts, converts and annotates — all locally, nothing uploaded.

Text-based PDFs convert almost perfectly. Scanned files need OCR first; pick the language under Tools → OCR.