While there are limited dedicated "one-click" web tools specifically for merging DWF (Design Web Format)
The most reliable methods involve using established desktop viewers that allow for manual sheet organization: Combining DWF files + filename labels - AUGI Forums merge dwf files online link
The solution is simple:
the files in the specific order you want them to appear in the final document. Click the "Merge" button to process the files. While there are limited dedicated "one-click" web tools