For companies that acquire other businesses or go through a period of accelerated growth, what recommendations, suggestions, or insights would you offer on effectively managing SOP documentation, process mapping, job aides, or work instruction development? What internal processes have you seen for properly maintaining process and procedure documentation?

Beyond the great comment already here, I'd add discipline from the board and leadership to add or hire experienced acquisition and integration manager(s), who did this before many times and know where corners cannot be cut.

Not consultants, experts.

The difference is that the expert will come and do it him/herself with the existing expertise and won't assign juniors after selling the work to the company.

This can make a huge difference in managing the additional workload for those working in the company and also pointing out fairly where you will need extra workforce instead of the usual "lump more work on existing FTEs while losing critical expertise by letting staff of the acquired company go too fast" approach.

For grounding, regardless of the scenarios, the mindset of documenting & maintaining procedures and policies is a culture that needs to be cultivated. There are tools, especially AI-powered ones, that can alleviate some of the effort; however, the culture needs to be ingrained and incented in the organization.

Specifically for environments with volatility and uncertainty, the first step is always to assess the current state of existing knowledge and policy assets. Eventually the goal is to standardize; however, the immediate priority is to ensure currency and completeness of the artifacts. Assuming a mature knowledge management framework exists, once the keys gaps are filled, harmonization and standardization can happen organically through regular maintenance activities. If a knowledge management practice is not mature, then it needs to be created immediately and prioritized based on risks.