Tinderbox - File Menu
Open the File menu, select Page Setup…
Open the Paper Size pop-up menu.
Paper Size Management
Select Manage Custom Sizes…
Custom Paper Sizes
Here, A0, A2, A1 sizes have been added. The aim is to have 'virtual' paper pages big enough to hold your Tinderbox maps. Here, large actual print sizes have been specified and the dimension can be set as desired and can the name given to the custom page. You could call yours "Tinderbox Maps" to remind you of the purpose.
Click OK when done. Then click OK to close the Page Setup dialog.
Using the Custom paper - size
When you come to print your map, use the File -> Page Setup and select one of your big custom pages. Above, an A1 page size is about to be selected.
Tip: if only doing this process occasionally, it's a good idea to reset the page when done to your normal page default which is likely US Letter in the USA and A4 anywhere else in the world.
Using the Custom paper - orientation
Normal default is for portrait printing (#1) whereas Tinderbox maps are probably a better fit on landscape orientation (#2). When done, you are ready to print to PDF.
As this process of printing to 'big' pages is an occasional one, don't forget to reset paper size and/or print orientation setting back to their normal defaults before you forget.
Extra credit step #1 - Cropping the PDF in Preview
Open your PDF in Preview. Select the 'select' tool and drag a bounding box around your image. You can zoom in if required to tweak the box dimensions. When the box looks good, go to Tools -> Crop (Cmd+K). Preview will warn you it's not actually deleting data and than show you the same file but only the contents of the cropped box. Tip: it can be useful to add an adornment with no name and fill colour as for the map background, drag it to encompass the map and set it as the back-most adornment. This will provide you with a marker to use when cropping the PDF – you can leave it in the subsequent image or crop just inside as you prefer.
Extra credit step #2 - Save for web as a PNG
Having cropped your PDF image, you can save it a web image for more easy re-use online. If you desire you can first save the PDF, so the above crop area is saved, otherwise this process will complete leaving the PDF file in its uncropped state (no right or wrong choice!). In Preview go to File -> Save as. Choose the location and filename and set the format to 'PNG'. Also consider dropping the pixels-per-inch setting from the default 150 to somewhere in around 72-100 . Going smaller will reduce file size at the loss of some text definition. Depending on your display needs, experiment for a setting that suits you. Click 'OK' and you now have a PNG ready to use as a normal web page image.