You can shift the order of your uploaded images so that the resultant PDF contain the images in the order you desire.
Simply drag and drop your choice of images and it will give you the desired PDF file. Make sure the images are not more than 20 in a single batch. Plus, each image should be maximum MB.
Convert X2Y do not permanently store any of your images on the server. All the images uploaded by you are deleted in the next 30 minutes. Nobody would have access to those.