Apple has an interesting video tip up this week on reducing the file size of graphic intensive PDFs created from the Print dialog. In their example they make a PDF from a Keynote presentation ...
Use Preview: Open the PDF in Preview, click File > Export, select “Reduce File Size” under Quartz Filter, and save. Use ColorSync Utility: Open the PDF in ColorSync Utility, click File > Export, ...
PDF readers and open-source libraries used in document processing will all need updating to handle the Brotli compression filter.