Technical drawing advice

[Sleepthief]

I'm hoping to change my front door, but because I live in a conservation area I have to apply for planning permission. Can anyone recommend a technical drawing app (for iPhone 6plus) that would be easy enough for a total novice to use just to create a simple image with measurements for the application? I don't want to fork out for idesign only to find it's idiot proof. I've attached the measurements and sketch I want to translate into something a bit more professional-looking to give you an idea of what I need. Thanks

[NotMeNoNo]

You could try graph paper and some fine liner pens? To look professional it needs to be to scale, 1:20 say, and have the date and title in a little box in the corner.

[Sleepthief]

Good call, thanks