I uploaded incorrect tax return file on IDOC website, I didn’t see anywhere how to remove the uploaded file.
[sarcasm]Don’t worry, IDOC is an incredibly user friendly and efficient service, with top-notch customer support. I’m sure that you’ll have everything figured out and corrected in no time.[/sarcasm]
Don’t worry about removing it. Just upload the correct one. It happens all the time! 
How are they going to know which one is correct? Also is it necessary to sign the tax returns, when you file with IRS there is no signature, so I forgot to sign, then scan and upload.
You could name the new file “corrected1040”. They do want the signature. Some mentioned using the pdf electronic signature. I printed, signed, and scanned. Someone was asked to resubmit with signature. There are a lot of other threads discussing details. Search for IDOC.
Can you use electronic signature though? Anyone can sign for anybody.
Use a real signature. As noted above, print, sign, scan, and then upload.
I don’t have a scanner, so I took a photograph of my signature, and I simply add that to any document requiring a signature. (I also don’t have the software needed to create or edit a .pdf file, so adding the signature is a rather time-consuming process, but it can be done.)