What to check before merging PDFs for a submission

When an application and its supporting documents have to go in as one PDF, check three things before you merge: the file rules set by whoever receives it, any password-protected files, and what merging leaves behind. Sort those out first and gather only the pages you need, in the right order. You’ll be much less likely to redo the file after it’s merged.

Check the submission instructions first

File rules often sit next to the list of required documents, in sections like “How to apply” or “Attachments.” Look for these before you merge:

What to check	What to do before merging
One combined file, or separate files per document?	If they want separate files, don’t merge
Document order	If an order is given, set your list to match it
Size limits (per file and in total)	If any PDF contains photos, check the merged size
File name rules	Look for a naming pattern or characters you can’t use
Password-protected files	Check whether they’re accepted

Grants.gov’s Applicant FAQs (checked 2026-09-30) show how specific these rules can get:

• Each federal agency sets its own file size limit, and Grants.gov suggests keeping the entire application package, including all attachments, to 200MB.
• If the agency or form sets no file name rules, names should be 50 or fewer characters and use only a listed set of characters.
• If two or more attachments have the same name, the application can’t be processed without manual intervention.

So limits can apply at more than one level, and even file names matter. If the rules are unclear and the submission is important, ask the recipient before you send it.

Unlock password-protected PDFs first

PDFs can carry a password. For example, when you save a Word document as a PDF, the “Encrypt the document with a password” option restricts access so only people with the password can open it (Microsoft Support).

Merge PDF doesn’t merge password-protected PDFs. As soon as you add one, that file alone shows “Password-protected PDFs can’t be processed” and is left out. Even a PDF that opens without asking for a password may show the same message if it has a password restricting printing or editing. If two or more other PDFs remain, you can merge them as usual; if only one is left, [Start] can’t be pressed.

If you made the document, save it as a PDF again with the password option off. If someone sent it to you, ask them for a copy without a password. A file that shows “The file is damaged or was not fully saved” couldn’t be read as a PDF, for example because a download was cut off. Save the original again, then add it.

What stays the same and what changes

Merge PDF doesn’t turn pages into images. It copies the text and images inside each PDF as they are, so quality doesn’t change. Some information that sits outside the page content, though, isn’t carried over.

Item	In the merged file
Page content (text and images)	Copied as is, same quality
Page rotation	Kept
Annotations	Kept
Bookmarks	Not carried over
Form fields	Not carried over
Document properties (title, author and so on)	Left empty

Form fields need the most attention. If you filled in a fillable form, open the merged file and make sure everything you typed still shows. Bookmarks used as a table of contents also disappear, so keep the original of any document that needs them.

The merged size isn’t always the sum of the originals. Merging our 3-page (2 KB) and 2-page (1 KB) test PDFs gave a 5-page, 1 KB file. Measured in desktop Chrome; results vary by device and browser. Merging doesn’t recompress images, though, so combining photo-heavy PDFs won’t make them smaller.

Pick only the pages you need, and make PDFs of photos and documents first

Merging includes every page of each file. If you need only some pages, pull them out first with “Extract into one file” in Split PDF. Page ranges look like 1-3, 5, 8-, where 8- means page 8 to the end. Entering 1-3, 5, 8-10 for our 10-page test PDF gave a 7-page PDF, measured the same way. For more on ranges, see How to save only the pages you need from a PDF.

Documents that aren’t PDFs yet should become PDFs first:

• Photos of paper documents or receipts: turn them into a PDF with Image to PDF, then merge. The steps are in Turn receipt and document photos into one PDF.
• Word documents: in Word, choose File, then Save As or Save a Copy, and pick PDF. Microsoft Support suggests “Standard (publishing online and printing)” when you need high print quality, and “Minimum size (publishing online)” when file size matters more. Leave “Encrypt the document with a password” off.
• If the merged PDF is over the size limit and many pages came from photos, shrink the original photos with Compress Image and rebuild the PDF.

How to do it with ZEKILO Studio

1. Open Merge PDF and drag and drop two or more PDFs or pick them with [Choose files]. Each file shows its page count and a thumbnail of its first page, and password-protected files are left out with a note right away.
2. Drag rows or use the up and down buttons to match the order the instructions ask for, then press [Start]. Files are merged from the top of the list down.
3. Save with [Download], then open the result and check the page order and any form entries.

Changing the order changes the result. With a 3-page file A and a 2-page file B, moving B to the top gives a 5-page PDF in the order B-1, B-2, A-1, A-2, A-3. The result is named merged.pdf by default. Turn on “Name after the first file” and it’s named after the top file instead, as in contract.pdf → contract-merged.pdf. Keep in mind that this adds 7 characters to the name. If the instructions set a naming rule, rename the file after you save it.

You can add up to 50 files at a time. We recommend a combined total of up to 200 MB on desktop and 50 MB on mobile, and files that would bring the total over 500 MB can’t be added. Your files are processed in this browser and never leave your device.

Summary

• Check the instructions for one file or several, document order, size limits, file name rules and whether passwords are allowed.
• Get password-free copies of any protected PDFs before you merge.
• Merging keeps quality, page rotation and annotations. It drops bookmarks and form fields and leaves document properties empty.
• Pull out only the pages you need with Split PDF, and turn photos and Word documents into PDFs first.
• After merging, check the page order, form entries, file name and size one more time before you submit.