Did you watch the video posted to youtube in the comment above by jthornburgh? He/she clearly shows the process that you say isn't possible. If you're having trouble seeing the details of what he/she's doing, use the video settings at the lower right corner of the video (the gear button) to increase the resolution of the video (all the way up to 1080p) and expand the video to "fullscreen" (the button that looks like corner brackets). By the way, you have to save any changes made to the assembly and the parts.
Can you send me a link? I never used youtube and there are some jthornburgh, can you send me a link? Thanks
You have to add the holes in just the part file by itself. If you need to do it in the assembly file you will still have to do it in each individual part, but you can right click on the part in the assembly and select edit part. Then anything you do will apply to the part you are editing. If you have one part that has the holes already and you want to transfer them to another part, edit the part you want to transfer them to, insert a sketch, then select all the edges of the holes that you want to transfer, and select convert entities. This will copy all the edges that you select into the current sketch. If you have external references on, the sketch will be fully defined and changing the first part will update the second part. If external references are off, the sketch will not be defined and changing the first part does not update the second. If you have any quires about Inventor , then you can see this video.<span style="background-color: rgb(250, 250, 250);"><font color="#333333">
