Previously, you could do a partition in LIVE-СD and save your data to USB (if LIVE-СD is loaded from USB.)
When booting from PXE you can mount any partition by NFS and save your data there.
Don’t you save your data (backup) in the cloud, a flash drive ?
Haven’t you lost it yet ?
For a long time many programs can save files to a remote resource (libre office) and many programs can be synchronized over the network (Firefox).
Using LIVE-CD is safer !
99% of the time you work with those packages that are already there and YOU do not tenderly every day something to delete and add.