Thank you.
Sejda has a lot of features and seems to be a solid tool. The big difference between Sejda's online tool and pdfux is that with Sejda (and most online PDF tools), your file is transferred over the internet to Sejda's server where it is stored, processed and sent back to you. Then they promise to delete it. Personally I am not 100% comfortable using this kind of tools with files that I wouldn't want to share with anyone. (I also see that Sejda has a desktop version for offline use which seems to be their answer to the privacy concern.)