Change Finder Printing default to print 100%, not scale to fit
If you drag and drop onto the Printer queue window, or otherwise send a job to print without settings the print options, then CUPS will fall back on the default options for that queue.

Check the manual to see if there's a way to set the default for your printer using its control panel, or other method. 

Failing that, you can set the default options for a specific queue in the CUPS web front-end. First, make sure that you can access the CUPS web interface:

cupsctl WebInterface=yes


Then in your browser, go to http://localhost:631

Click on Printers in the menubar at the top. Click on the print queue. Then choose Set Default Options from the 2nd drop-down menu. 


..

You may find a Fit To Page parameter, with options:



But the available options will depend on the definable characteristic of your printer. The fact that it is scaling suggests it does have such a setting.

As for the lp command: that command sends files to a print queue, and you can specify the job options that are used. To find the appropriate options, use:

lpoptions -l &lt;printQueueName&gt;


The print Queue Name is optional for the default printer.

So, for my HP LaserJet, I get (among other things)

HPPaperPolicy/Fit to Page: PromptUser *NearestSizeAdjust NearestSizeNoAdjust


The asterisk shows the current default. If I wanted to change that for a specific file, I would use:

lp -d &lt;printQueueName&gt; -o HPPaperPolicy=NearestSizeNoAdjust /path/to/file


Again, you don't need the -d flag to set the destination if it's the default printer.