I think this is usually done

I think this is usually done with plans drawn in xTrackCAD or similar programs, where you can print the plan at full size with your home printer and tape the pages together.

Print Shops

Print Shops are not as common as they once were but a place that does large format prints, formerly known as blueprints, would be your best bet. Check with a local drafting or blueprint company to see what they would charge if you want big sheets.

A lot of guys are happy working with a number of 8-1/2 x 11 sheets taped together. Even 11 x 17 would be ok but you will have a little work to do.

First, your software must be able to print sheets to a full size or allow you to print in sections. If you are working from a sketch or published plan then it will need to be scanned and scaled to the size you need. For example, the published plan is noted as 1/4" = 1'-0". This would be scanned and scaled to full size by enlarging to match the scale published (note that a graphic scale is helpful here so that you can measure a small section printed to size). 

Some software, like AutoCad, will allow you to create paper sheets that have the plan enlarged to full size and only a portion printed on that sheet. This would allow you to create a number of sheets that overlap to some degree for registration / alignment. Other programs do this automatically.

So start by getting the plan scanned. Have a small portion printed at full size and be sure that the scale is correct. I wish I was closer and could help. My printer is 18" wide and can print as long as needed. Your local "blueprint" shop may be able to do something similar.

also sign shops

If you're looking for large format prints, once you have your plan scanned and sized, you can also take it to a sign shop for printing.

Most sign shops in my area will print black and white at a reduce price per sq ft. Color printing is generally quite pricey.

My local shop has a 60" printer. I've seen up to 120" wide printers. The length of the print is basically unlimited and have the shop use the cheapest paper for this type of work.

Enlarging plans

Try FedEx shops that are ex-Kinko's.  Back when I was doing commercial layout design, they had copy machines that were capable of scaling plans as well a just making straight copies.

 "where to get my layout plan

I'd just draw a one foot grid on the plan then scale it and transfer it right to  the layout room floor or benchwork if that can be built first. Once the center lines are drawn paper patterns would just be in the way. The main points to scale and transfer are radius points, beginning and end of curves,  turnout points of frogs ,etc. the rest can be filled in from these control points. Pretty much how a real railroad would do it.......DaveB

Dave’s on the right track, as usual....

To save the cost of printing and rebuying software even Sharpie points the grid crossings on the 1 foot squares should be enough to copy your plan.  A flexible stick through a few points should give the easements,

Save your money for a nice locomotive.

Nick

$30

at Staples with a coupon for 2x8 banners from a PDF. The cost of my time at laying out a grid and copying points with sticks and such is way more than that. Then use a pounce wheel and bag to transfer your lines.

Engineering or Blueprint Prints

Having done some small projects connecting 4 to 6 sheets of  11x17 prints, I would suggest going for the largest size you can afford.  Stapes will print 24x36in engineering drawing for $3.60 each. There are a number of free PDF printing programs that will generate the files needed.  You could also search for printing services for blueprints or engineering drawings; found one in WA that charges $0.30 sq.ft. for up to 300 sq.ft..

I printed my trackplan out full scale myself

I use SCARM to printout my track plan full size even though it didn't have a "print full scale" option.  It took some time to trim & tape the sections together but was well worth it.