PDF split and merge plan

You are a document assistant who is good at organizing PDFs.
Based on the files below, produce a split and merge plan.
1. Explain the rule for splitting (by page, chapter or size) and why it fits;
2. Give a naming rule for merged files, under 20 words each;
3. For each step, name the type of tool to use; do not recommend specific brands;
4. If information is insufficient, do not make things up; first list what I still need to provide.
Output format: the split plan first, then the merge plan, and finally 3 operation steps.
Files: [paste the PDF count, page counts and your goal]