How do i fix "A binary attachment submitted in the PDF format must begin with the file header "%PDF-"

UPDATE: FIXED! (ymmv)  [error code reject code  X0000-029]

Short answer: I deleted my 1099B broker statement summary entries and reloaded them in DETAIL (luckily I was able to import them from my brokerage account but I was prepared to enter by hand). I recalled TurboTax asking me about data to support Form 8453 and I believe I uploaded my brokerage pdf [or I was dreaming].  Entering the DETAIL data precluded this requirement and the IRS accepted by tax return.

Long answer: forms 1099B are the culprit: After much back and forth with the turbotax people I started to go thru my paper printout scanning each schedule for FORM names and looking them up to see WHERE I was asked to upload a pdf so I could change it.  When I got to form 8949 that is when I realized I entered SUMMARY data and TurboTax prompted me that I would have to mail in a copy of the details and use Form 8453.  But I also recall TurboTax asking for me to upload a pdf copy.  I believe I did this.  I tried over and over to manipulate the data on the summary data entry to force TT to re-prompt me to mail in the forms and to upload the pdf to no avail.   I went ahead and deleted all the entries and resigned myself to enter in pages and pages of data if the electronic import would not work (I couldn't get it to before).  The electronic import brokerage lookup process is horrible.  If I type "pershing" I get two entities but if I type "pershing llc" I get complete DIFFERENT entities.  and in my case, NMIS.. was the correct one (northwestern mutual 'something something' - which is no where on my statements (but I am "with" northwestern mutual).  In the end, putting in the details for my stock sales negated the need to mail the IRS a copy and negated turbotax asking for a pdf upload.

TURBTAX - IF YOU ARE LISTENING:  this is where the issue is - WHY do you not expose the fact we uploaded a document here - why not have a section in "mydocs" that shows files you are going to send the IRS on our behalf? Lastly, why do you dead end this error message?

I ran into this problem as well. It stumped me last year, and I had to reluctantly print and mail my taxes. This post helped me figure it out, but here's how I did it.

For me, it was also due to 1099s that Turbo Tax asked me to upload. I went through each entry in Turbo Tax by clicking Edit and then opened each PDF that I had uploaded locally on my computer in a text editor (TextEdit on a Mac). Most of them had %PDF-1.3 or %PDF-1.5 as the first line of the file, which I believe is what the IRS is checking for to see that the file is a valid PDF file. Then I found one file that had the following at the beginning of the file:

--MIMEBoundaryurn_uuid_[phone number removed][phone number removed]

--MIMEBoundaryurn_uuid_[phone number removed][phone number removed]
Content-Type: application/pdf

Which was the problematic file, which happened to be from Northwestern Mutual. So I opened in the Preview app on my Mac and re-saved it (File > Export as PDF). You should be able to do an equivalent of this on Windows with Adobe Acrobat by printing to PDF or doing a Save As (not sure, but I'm sure there's a way). Then I verified that the new file started with %PDF-1.x, and then deleted the file in TurboTax and re-uploaded the fixed one. That did the trick! Hopefully that's helpful to someone who's running into this same problem.

TurboTax folks - it would be nice if TurboTax verified the validity of PDF files just like the IRS does, so users don't get into this strange state, or even repaired the files for us. 

This was an incredibly helpful post. My returns been rejected 4 times, including twice after calling turbo tax and getting told to just re-upload the form. It doesn't make any sense that the Northwestern digital connection can't be found by searching for Northwestern or that different results appear when typing Pershing vs Pershing LLC in the search.

Thanks for your help. Cured a significant headache.

Thank you, this post was super helpful! 

This suggestion might save a little time for people.  Instead of having to manually enter everything, I used the Preview App on my mac to open the Pershing document.  Within Preview, there is an option to "Export to PDF."  Apparently doing the "Export to PDF" option on the original PDF I downloaded from the website rewrites the file headers, because afterwards, I was able to successfully submit my return.  I'm not sure, but I would think PCs would have a similar option somewhere.  

Hope this helps.