While working on Adobe Photoshop, some time you get several type of errors “PSD file corruption” errors are one of then. Some time when you try to open a photoshop file (.psd) you get a error message which “Could not complete you request because it is not a valid Photoshop document”. This message means that your file is not in proper format which can be recognize by photo shop. This means that header part of your photoshop file is get corrupt, damaged or changed thats why photoshop not able to open it. In this case you need to apply some method to fix header part of your .psd file or use PSD repair software.
Here I am explaining a real case which is faced by one of my friend. He have same problem, he try to compare hex code corrupt PSD files with normal PSD file. He found that due to unknown reason, Photoshop is adding few extra bytes in the beginning of PSD files at the time when you save. The same photoshop give error when you try to PSD file created with it. Since signature of PSD file is get change due to these extra bytes thats why Photoshop could cot recognise these files. To fix this error you need to remove these extra bytes with the use of Hex editor.
Assuming that you already know what is a HEX editor (WinHex) and how to use it I'll write here a few steps you can do before opening a "corrupt" PSD file:
1 - Make a back-up (copy) of the file before making any changes.
2 - Open the "corrupted" file in an usual HEX editor (NOT text editor!) and look for such groups of character just in the beginning: 8BPS and after a few bytes 8BIM another group of bytes and again 8BIM.
3 - This succession should be respected strictly: 8BPS ... 8BIM ... 8BIM. These groups should be very close to each other and it's easy to find them.
4 - Delete all bytes before 8BPS group (Shift+Delete) and save the file.
5 - Open it in Photoshop and Enjoy.
The above method will surely resolve your problem of “Could not complete you request because it is not a valid Photoshop document” . But due to any reason if your problem persist then go with PSD repair software to fix your problem.