Unable to manipulate downloaded .stp file

[SSHotMixParts]

See image below. I can't seem to figure out why I cannot manipulate this file. All tool bars are blacked out like it has the "read only" property. Which was first thing I checked to try to diagnose this issue. I've also tried save copy as, checking in & out of the Vault. Deleting local copies and opening from Vault. Even re-downloading the same file. Nothing seems to work. Is there something I'm doing wrong? Or did whoever create this remove the write capablity from it somehow. All I am trying to do is go into document settings and change the units from metric to standard. Any and all help/input is greatly appreciated! Thanks!

[jtylerbc]

That doesn't look like a STP file.  That looks like a native Inventor model, consisting of an iPart child.  The fact that it is an iPart child is the reason you can't edit the model.

Parker usually posts their files in several formats, one of which actually is .STP.  If this was downloaded from the Parker website, if you download the .STP instead of the .ipt version, you will probably be able to edit it.