Here's how I get this extension to work.
1. Download the oracle-pdfimport.otx file to any location (I downloaded it to my Downloads folder).
2. Open Finder, on the left side of the Finder window click 'Applications', and locate OpenOffice.org.app (but don't open it -- i.e. don't double-click it).
3. Single-click the OpenOffice.org.app to highlight it. Next (and here's the important part) hold down 'control' key at the bottom left of your keyboard, and while holding down the 'control' key click on your trackpad --> this will bring up a context menu --> from this context menu click 'Show Package Contents'.
4. You will now see all the folders and files that are used by the OpenOffice.org.app. BE VERY CAREFUL IN THIS STEP not to accidentally move or delete any of these folders or files...the app needs them all.
5. Continuing from Step 4, in the Finder window you will see a folder named 'Contents'. Click the arrow to the left of the 'Contents' to expand it and see the folders and files contained within it. After you've expanded the 'Contents' folder, immediately beneath it you'll see a folder named 'share' --> click the arrow beside 'share' to expand this folder. Under 'share' you will see a folder named 'extensions' --> click the arrow beside 'extensions' to expand it. Lastly, there is a folder under 'extensions' named 'install' --> click the arrow beside 'install' to expand it.
6. Continuing from Step 5, inside the 'install' folder you will probably see a file named 'dict-en.oxt' that automatically installs with OpenOffice. This 'dict-en.oxt' file has a file icon that looks like a puzzle piece (apparently that's the icon OpenOffice chose to use for extension files).
7. Now look at the Finder menu bar at the top of your Mac's screen. Click 'File', then click 'New Window'. This will cause a new Finder window to open. Now you have 2 Finder windows open: 1 window that has the contents of your OpenOffice.org.app, and the new window you just opened. Move (drag) each of these 2 Finder windows so that you can see both at the same time on your Mac's screen. Now, in the new Finder window you opened, navigate to the folder where you downloaded the PDF extension file named oracle-pdfimport.otx (in my case, since I saved it to my 'Downloads' folder, on the left side of the Finder window I click my name -- it has a little icon beside it that looks like a house -- then to the right of that I find and click on my 'Downloads' folder, then I scroll through the files in that folder and find the one named oracle-pdfimport.otx. Single-click on the oracle-pdfimport.otx file and drag it over to the other Finder window from Step 3 which shows the contents of the OpenOffice.org.app folders and files. Drag the oracle-pdfimport.otx file into the 'install' folder from Steps 5 and 6 and drop it into that folder. You should now see at least 2 files in your 'install' folder; both files will have the icon that looks like a puzzle piece. 1 file will be the dict-en.oxt that was mentioned in Step 6, and the other file will be the oracle-pdfimport.otx that you just dragged into that folder.
8. Once you've verified that the oracle-pdfimport.otx file got dropped into your 'install' folder, close the 2 Finder windows you opened. This is just for safety, since you don't want to muck around any further in the window that shows the package contents of the OpenOffice.org.app.
9. Whew! Now you're done. Because you placed the oracle-pdfimport.otx inside your 'install' folder, the next time you open the OpenOffice.org.app, the oracle-pdfimport.otx extension file will automatically load and be ready to use. Since the new extension automatically loads when the app starts up, you don't have to do anything after the OpenOffice.org.app opens to enable the extension. It's already loaded and ready to go!
9. Now to test the extension. After you've completed all of the above steps, start the OpenOffice app from your 'Applications' folder, and when it loads, click the 'Open' button on the start-up screen and navigate to a wherever you have a PDF file stored on your Mac. (If it's an important PDF file, be sure to make a copy of it before you open it.) When the PDF file opens inside the OpenOffice app, whatever text or image you click on will display a box around it; you can choose to either click somewhere inside the box to edit its text, or you can hover your mouse around the box until the cursor changes to a hand and then you can use the hand to drag the 'boxed' text or image to any place you like inside the PDF document. That's about it. From there, you just have to play around with it to see how you can edit text and move things to your liking. When you're done playing with a file, you can choose to save it or discard the changes you've made.