How should I choose an online PDF tool?

Look at the nature of the job before ranking the tools. If the material is fine to share openly and you only need to merge it once, whatever you already know works. If a submission spec is attached, the question becomes whether you can control file size and page order. If the paperwork contains an account number or a resident registration number, the question becomes whether you can cover those fields before anything else. Every service documents how it handles files and how long it keeps them, so read the official notice yourself before you upload.

My pages came out in the wrong order after merging

That is filename sorting at work. Names like 1, 2 and 10 look sequential to a human, but sorted by name they line up as 1, 10, 2. Drag the pages into place on screen after uploading, or pad the filenames to a fixed width such as 01 and 02 before you upload, and the problem disappears.

I compressed the file and the size barely moved

Most of a PDF's weight comes from the images inside it. A PDF built mainly from text is already light, so there is little left to squeeze. Paperwork made from photographs, on the other hand, compresses a great deal. Compressing an already compressed file only degrades the picture while the size stays roughly the same, so run it once on the original.

Can the recipient undo the covering I applied?

If the cover is merely sitting on top of the original, the recipient can lift it off. That is why covering is followed by flattening, which bakes the page into an image or rebuilds it as a PDF so the layers are gone. The point is that not visible on screen and not present in the file are two different things.

Which rung are you on? - Browser PDF workflow in 3 tiers

Hand-drawn three-panel illustration of a stack of PDF files growing tidier from left to right

A browser PDF workflow feels different every time, and the reason is not the tool but the paperwork in front of you that day. Yesterday two files went out the moment they were merged; today an upload limit blocks you, and tomorrow an account number has to be covered first.

Even a plain "merge PDF" job turns into an entirely different task depending on how many steps attach to it front and back. Once you can name the rung, you stop guessing at the order.

Hand-drawn illustration of three panels side by side: two sheets overlapping into one, a ruler and scales, and a document with part of it blacked out — The same files call for different hands on a merge day, a spec day, and a covering day.

Seven minutes will get you

A way to judge for yourself whether today's paperwork is tier 1 or tier 3.
The right order for merging, splitting, compressing and rotating.
A finish that stops sensitive fields from being uncovered again.

Difficulty in a browser PDF workflow is not set by how many files you have but by what is attached to the paperwork. A spec attached makes it tier 2; personal data attached makes it tier 3.

Which tier is your browser PDF workflow today?

There are three tiers. Each one adds work, and what raises the tier is never the file count but the conditions attached to the document. Picture the file you have to send right now and read down the list.

Tier 1 · One pass and it is done

Merge it, or split it. That is the whole job

Scattered files just need to be bundled into one and sent. Three meeting handouts becoming a single file, or pages 3 to 5 lifted out of a twenty-page document, both live here. With no conditions attached, there is no order to agonise over.

Drop the files into Merge PDF and set the sequence; to pull out only the pages you need, set a range in Split PDF. If all you have is photographs of the material, run them through Image to PDF first to get one file.

Tier 2 · Meeting a submission spec

"Under 10MB", "in order", "the right way up"

The moment the recipient dictates the shape, you are on tier 2. An upload size ceiling, the page order, even the direction a sideways scan is facing all have to line up before it will be accepted. This is where documents bounce for their form, not their content.

Size is handled by Compress PDF, and a sideways scan is straightened with Rotate image. If the text itself needs editing, move it through PDF to Word, fix it there, and turn it back into a PDF.

Tier 3 · Sensitive data in the mix

Cover it, bake it, then submit

Bankbook copies, ID cards and payslips are documents that carry fields the purpose never needed. Here, merging is not the first move: covering comes first, and covering is followed by one more step.

Use Privacy masking to cover what has to go, bake the result into an image so the cover cannot be lifted, and only then bundle it. The full order is spelled out further down.

Tier	What is attached	Where it fails
Tier 1	Nothing. The files are simply scattered	Pages out of order, so you resend
Tier 2	A submission spec: size, order, orientation	Rejected at intake for not matching
Tier 3	Personal data that has to be covered	The cover is lifted and the data shows

The mistake tier 1 makes most often

Merging is the simplest thing in a browser PDF workflow, and yet it is resent more than anything else. The cause is almost always the same one: order.

Upload several files and they usually queue up by name. But 1.pdf, 2.pdf and 10.pdf sort as 1, 10, 2, which is not the order a human reads them in. Checking the sequence on screen after uploading is the single habit that makes this disappear.

To head it off in advance, pad the filenames to a fixed width, 01 and 02 rather than 1 and 2. Past twenty files this is far and away the easier route. For sorting a bundle of documents by their state, we covered that separately in Organising supporting documents into a PDF in three steps.

Tier 2: why size and orientation come last

Two-row hand-drawn comparison: the top row shrinks each document first and then merges, ending blurry, while the bottom row merges first and shrinks once, ending sharp — Shrink first and the quality lost before merging never comes back.

Invert the order and you pay for it. Compression is a trade: picture quality out, file size in. Shrink each file once and then merge, and you make that trade as many times as you have files.

Merge first and shrink once, and the trade happens once. Compress at the very end, once, on the original. Running compression over an already shrunken file only makes the picture worse while the size sits roughly where it was.

Orientation works the same way. If a scan came out sideways, stand it up with Rotate image before merging. Notice it afterwards and you have to split the file apart again to fix it.

Orientation first: stand up any sideways scans before you begin
Then bundle: confirm the sequence on screen in Merge PDF
Compress last: run Compress PDF once, on the finished file

Some places want images rather than a document. When a preview has to go up on a message thread or a notice board, PDF to image gives you one picture file per page.

Tier 3: why a cover can be lifted off

Hand-drawn comparison: on the left a black rectangle floats slightly above the document with movable handles at its corners, on the right the same rectangle is pressed flat into the paper — A black rectangle that is only laid on top can be pushed aside by whoever receives it.

This is the step most often missed. A black rectangle goes over the number, and on the recipient's screen it slides away and the original digits are back.

The cause is layers. Drop a shape onto a page in an editor and that shape stays as a layer separate from the text underneath. The screen shows it covered while the file still holds the layer below. Not visible on screen and not present in the file are two different things.

So covering has to be followed by flattening, which removes the layers. Written as a sequence, it goes like this.

Step 1

Cover what the purpose does not need

In Privacy masking, cover things like part of an account number or the back half of a resident registration number: fields the submission does not need. Which ones are mandatory differs by recipient, so read their guidance first.

Step 2

Bake it into an image so the layers go

Save the covered result as an image and rebuild it with Image to PDF, and the covered patch becomes part of the picture. There is no longer a layer to push aside.

Step 3

Only now bundle and shrink

Take the finished file into Merge PDF, and if size is a constraint, run Compress PDF once at the end. If the document needs a seal, Stamp a PDF belongs in this same step.

How far to cover is not a matter of instinct; there is a standard. Article 3(1) of the Korean Personal Information Protection Act requires a personal information controller to lawfully collect only the minimum personal information within the scope necessary for the processing purpose.

That is your grounds for covering a field the recipient never asked for.

How do you pick a tool?

There are plenty of online tools for a browser PDF workflow, and many people already have one they know by feel. Rather than asking which is better, it is more accurate to ask whether it has the conditions the job calls for.

Your tier	What to check
Tier 1	Can you change the order directly on screen?
Tier 2	Can you set the compression strength and page range yourself?
Tier 3	Can covering and flattening be finished in one flow?

If you want to know how files are handled or how long they are kept, reading each service's official notice yourself is the most accurate route. Policies change, so it is worth checking at the moment you use it.

In one line

In a browser PDF workflow the tier is set by conditions, not by file count. No conditions and you merge and you are done; a spec attached and orientation and size come into it; personal data in the mix and you cover, bake, then bundle. Know the order and you stop getting lost every time.

If you have a file to send right now, you can start straight away in Merge PDF.

References

Personal Information Protection Act (Republic of Korea), Article 3 (Principles for Protecting Personal Information), paragraph 1. Korean Law Information Center
Personal Information Protection Commission, Personal Information Portal (privacy.go.kr)

This article is for general information only and is not legal advice. The legal provisions referred to are current as of the time of writing (August 2026), and the mandatory fields of a submitted document, along with what may be covered, vary by recipient and by the applicable statutes, so follow the recipient's official guidance for your specific case. The features and policies of third-party services may change, so check each service's official notice before use. Use the covering features described here only on documents you are authorised to submit.

Frequently asked questions

: Look at the nature of the job before ranking the tools. If the material is fine to share openly and you only need to merge it once, whatever you already know works. If a submission spec is attached, the question becomes whether you can control file size and page order. If the paperwork contains an account number or a resident registration number, the question becomes whether you can cover those fields before anything else. Every service documents how it handles files and how long it keeps them, so read the official notice yourself before you upload.
: That is filename sorting at work. Names like 1, 2 and 10 look sequential to a human, but sorted by name they line up as 1, 10, 2. Drag the pages into place on screen after uploading, or pad the filenames to a fixed width such as 01 and 02 before you upload, and the problem disappears.
: Most of a PDF's weight comes from the images inside it. A PDF built mainly from text is already light, so there is little left to squeeze. Paperwork made from photographs, on the other hand, compresses a great deal. Compressing an already compressed file only degrades the picture while the size stays roughly the same, so run it once on the original.
: If the cover is merely sitting on top of the original, the recipient can lift it off. That is why covering is followed by flattening, which bakes the page into an image or rebuilds it as a PDF so the layers are gone. The point is that not visible on screen and not present in the file are two different things.
: The principle is to cover anything the submission does not need. Article 3(1) of the Korean Personal Information Protection Act requires a personal information controller to collect only the minimum personal information within the scope necessary for the processing purpose. If the recipient did not ask for a field, you may cover it. Which fields are mandatory differs by recipient, so check their official guidance before you erase anything.

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