How to convert PDF/A to normal PDF?

You don't tell us, but I assume it: you are using Adobe Acrobat in order to 'crop' your PDF/A? Which exact version is it?

Anyway, in the Preferences > Document settings, you can switch off a Display PDF/A in PDF/A-mode.

Once you've done that the blue horizontal band informing you about the PDF/A property of the file at the top of each page will disappear, and it will be possible to manipulate the file. (You may need to re-open the PDF).

Once manipulated (and saved), the PDF/A property will be lost anyway.

Viewing PDF/A files in PDF/A-mode prevents Acrobat from changing the file (since PDF/A is for archiving).

If you just wish to convert the PDF/A to a normal PDF, and save it for later editing, you can use Adobe Acrobat as suggested by user Mrtymccarter on Jun 26 '12. This is a follow-up on the comment made by Canadian Luke on Sep 25 '13, to include essential parts of the answer.

Instructions (Adobe Acrobat XI)

1. Open the Tools side bar and choose Action Wizard.
2. Choose Create New Action...
3. Choose Document Processing -> Preflight and add it to the action steps on the right side.
4. Choose Specify Settings. (Recommended: uncheck Prompt user)
5. Below Run Preflight check using, select Remove PDF/A information and click Save.
6. (Optionally add other features, such as asking to save the PDF after running the action)
7. Save and name the action, e.g. 'Remove PDF/A'.

The newly created action should be available below Action Wizard -> Actions.

Click it to remove PDF/A information.

(As described in the previously posted Adobe blog post)

You can also remove it in Foxit PhantomPDF - it is much better then Acrobat: fast, less weight, it remembers last opened page for any pdf (Acrobat doesn't remember it for any pdf file, only some)

How to remove PDF "A" infomation in "Foxit PhantomPDF":

1. open file in PhantomPDF
2. click on "convert"
3. click on "industry standart"
4. check "PDF/A comliance"
5. double click "remove PDF/A inforamtion"
6. save new file