The preferred way to do that is to use readAllFootersInParallelUsingSummaryFiles().
It will use the _metadata (summary) file that contains all the footers and makes is faster to read than reading the footers from the part files. For now it enforces that the schema is the same for all files, In the future we will want to read multiple directories at once an handle schema compatibility (most recent schema is a superset of previous ones)