src/Merger.php
public function addIterator(iterable $iterator, PagesInterface $pages = null): void
    {
        foreach ($iterator as $filename) {
            $this->addFile($filename, $pages);
        }
    }
public function addIterator(iterable $iterator, PagesInterface $pages = null): void
    {
        foreach ($iterator as $filename) {
            $this->addFile($filename, $pages);
        }
    }
Add files using iterator

Note that optional pages constraint is used for every added pdf