Do you have a PDF copy of your 2018 return? I assume you do so open your return in Adobe Acrobat.
Scroll through the return. You want to print the 1040, Schedules 1-5 (if you have them, most people don't have all of them), and any other IRS forms, like Schedules B, C, SE, E, etc.
You do not need to print the filing instructions or the worksheets (I think all of them say "Worksheet" at the top).
If there are printed copies of your W-2 or any 1099s, then also print those. In Acrobat, you can choose which pages you print by choosing the page or range of pages in the print dialogue.
Otherwise, if you used the CD/download software in 2018 and still have it, open your .tax2018 tax file and click on the link Print Center at the far upper right (hard to read). Choose the first option "All official forms required for filing". Save them as a PDF (with a different name from the previous PDF), and then open the PDF and print them. You should now have only the forms required for filing (but it's good to have the full document set for your own records).
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You will only file most pages above the "Tax history Report".
There might be a few above that are not filed (as previously noted...like the Filing Instructions), but nothing below it.
The first page of any forms that must be printed and filed will have an "Attachment Sequence No" in the upper-rt corner of the form (2nd or subsequent pages of the same form must be printed and filed, but they don't have the seq # in the upper rt corner)
Any Quarterly Estimated tax forms might also be at the top of the PDF, but those aren't filed if present at the beginning of the PDF......and sometimes there is a "State and Local Income Tax Refund Worksheet" just above the Tax History Report that is not filed.
To be clear, W-2 forms and any other tax forms (W-2G,1099-??? forms, etc) that show tax withholding on them must be included with your filing...but the copies of those in your tax file PDF are only software worksheets...and you must use copies of the originals that were sent to you by the issuer, or separate PDF copies of the originals that you download from the issuer's websites.