When I download the tax forms, the 1040 doesn't render completely - lines 23 through 56 are missing in the pdf. How do I get a complete pdf download?

[xmasbaby0]

Not everyone will have all of those forms.  The new Form 1040 is a "postcard" size form that prints out as two half pages on one sheet of paper.  Then there are 6 possible extra schedules.  You will not necessarily have all of those schedules.  It depends on what kind(s) of income etc you entered.  It may be that you did not use Schedules 1, 2, or 3, which would account for why those lines are not in your printed tax forms.

The tax forms are different for 2018 and beyond since the new tax laws went into effect.  Everyone gets a "postcard size" Form 1040 that only goes to line 23. In addition, there are six possible extra pages called "schedules" that may be included as part of the tax return that you prepare and file.

https://www.irs.gov/pub/irs-pdf/f1040.pdf 

https://www.irs.gov/pub/irs-pdf/f1040s1.pdf

https://www.irs.gov/pub/irs-pdf/f1040s2.pdf 

https://www.irs.gov/pub/irs-pdf/f1040s3.pdf 

https://www.irs.gov/pub/irs-pdf/f1040s4.pdf 

https://www.irs.gov/pub/irs-pdf/f1040s5.pdf 

https://www.irs.gov/pub/irs-pdf/f1040s6.pdf 

[VolvoGirl]

There are no more lines after 23.  

Yes that is the NEW postcard size 1040.  Under the new tax laws, there are no more simple Form 1040EZ or 1040A's.  Everything goes on a little Form 1040 that has six extra "schedules" with it.

The new 1040 is 2 half pages but now print on 1 sheet with the Signature line in the Middle.

Wages is on line 1.

The AGI and total income is now on line 7.

Standard or Itemized Deductions is line 8.

Taxable income is on line 10 and Tax on line 11.

https://www.irs.gov/forms-pubs/about-form-1040