documentclass{article}
pdfminorversion 4
immediatepdfobj stream attr{/N 3} file{sRGBIEC1966-2.1.icm}
pdfcatalog{%
/OutputIntents [ <<
/Type /OutputIntent
/S/GTS_PDFA1
/DestOutputProfile thepdflastobjspace 0 R
/OutputConditionIdentifier (sRGB IEC61966-2.1)
/Info(sRGB IEC61966-2.1)
>> ]
}
usepackage{xcolor}
usepackage{hyperxmp}
usepackage[pdftex, pdfa]{hyperref}
hypersetup{%
    pdfauthor          = {a},
    pdfkeywords        = {a, b, c},
    pdflang            = {en},
    pdftitle           = {a},
    pdfsubject         = {a},
  pdfcaptionwriter   = {a},
  pdfcontactaddress  = {a},
  pdfcontactcity     = {a},
  pdfcontactcountry  = {a},
  pdfcontactemail    = {a},
  pdfcopyright       = {a},
  pdfmetalang        = {en}
}
usepackage{amsmath}
usepackage{lipsum}
begin{document}
tableofcontents
section {A}
{color{blue}Hello} World!
[1+2=3]

section {B}
lipsum
(1+2=3)
begin{align*}
A &= B\
  &= C\
  &= E
end{align*}

newpage

section {C}
lipsum
[1+2=3]
end{document}

The file test.pdf is a valid PDF/A-1b file

documentclass{article}
pdfminorversion 4
immediatepdfobj stream attr{/N 4} file{ISOcoated_v2_eci.icc}
pdfcatalog{%
/OutputIntents [ <<
/Type /OutputIntent
/S/GTS_PDFA1
/DestOutputProfile thepdflastobjspace 0 R
/OutputConditionIdentifier (FOGRA39L)
/Info(FOGRA39L)
>> ]
}
usepackage[cmyk]{xcolor}
usepackage{hyperxmp}
usepackage[pdftex, pdfa]{hyperref}
hypersetup{%
    pdfauthor          = {a},
    pdfkeywords        = {a, b, c},
    pdflang            = {en},
    pdftitle           = {a},
    pdfsubject         = {a},
  pdfcaptionwriter   = {a},
  pdfcontactaddress  = {a},
  pdfcontactcity     = {a},
  pdfcontactcountry  = {a},
  pdfcontactemail    = {a},
  pdfcopyright       = {a},
  pdfmetalang        = {en}
}
usepackage{amsmath}
usepackage{lipsum}
begin{document}
tableofcontents
section {A}
{color{blue}Hello} World!
[1+2=3]

section {B}
lipsum
(1+2=3)
begin{align*}
A &= B\
  &= C\
  &= E
end{align*}

newpage

section {C}
lipsum
[1+2=3]
end{document}

5.2.3 : Forbidden field in an annotation definition, Annotation uses a Color pro
file which isn't the same than the profile contained by the OutputIntent

A device-specific color space (Annotation C or IC) without an appropriate output intent is used.
The document does not conform to the requested standard.
The document contains device-specific color spaces.

documentclass{article}
pdfminorversion 4
pdfcompresslevel=0
immediatepdfobj stream attr{/N 4} file{ISOcoated_v2_eci.icc}
pdfcatalog{%
/OutputIntents [ <<
/Type /OutputIntent
/S/GTS_PDFA1
/DestOutputProfile thepdflastobjspace 0 R
/OutputConditionIdentifier (FOGRA39L)
/Info(FOGRA39L)
>> ]
}
usepackage[cmyk]{xcolor}
usepackage{hyperxmp}
usepackage[pdftex, pdfa]{hyperref}
hypersetup{%
  colorlinks = true,
    pdfauthor          = {a},
    pdfkeywords        = {a, b, c},
    pdflang            = {en},
    pdftitle           = {a},
    pdfsubject         = {a},
  pdfcaptionwriter   = {a},
  pdfcontactaddress  = {a},
  pdfcontactcity     = {a},
  pdfcontactcountry  = {a},
  pdfcontactemail    = {a},
  pdfcopyright       = {a},
  pdfmetalang        = {en},
}
usepackage{amsmath}
usepackage{amsthm}
usepackage{amsrefs}
usepackage{lipsum}
theoremstyle{plain}
newtheorem{theorem}{Theorem}
begin{document}
tableofcontents
section {A}
{color{blue}Hello} World!
begin{theorem}
label{thm.1}
begin{equation}
1=1label{eq.1}
end{equation}
end{theorem}
begin{proof}
By reflexivity of (=).
end{proof}
Theorem ref{thm.1} is about the equation eqref{eq.1}.
See also cite{MR1727844}.
begin{bibdiv}
begin{biblist}
bib{MR1727844}{book}{
   author={Bourbaki, Nicolas},
   title={Algebra I. Chapters 1--3},
   series={Elements of Mathematics (Berlin)},
   note={Translated from the French;
   Reprint of the 1989 English translation [ MR0979982 (90d:00002)]},
   publisher={Springer-Verlag, Berlin},
   date={1998},
   pages={xxiv+709},
}
end{biblist}
end{bibdiv}
end{document}

documentclass{article}
pdfminorversion 4
pdfcompresslevel=0
immediatepdfobj stream attr{/N 4} file{coated_FOGRA39L_argl.icc}
pdfcatalog{%
/OutputIntents [ <<
/Type /OutputIntent
/S/GTS_PDFA1
/DestOutputProfile thepdflastobjspace 0 R
/OutputConditionIdentifier (Coated FOGRA39)
/Info(FOGRA39L)
>> ]
}
usepackage[cmyk]{xcolor}
usepackage{hyperxmp}
usepackage[pdftex, pdfa]{hyperref}
hypersetup{%
  colorlinks = true,
    pdfauthor          = {a},
    pdfkeywords        = {a, b, c},
    pdflang            = {en},
    pdftitle           = {a},
    pdfsubject         = {a},
  pdfcaptionwriter   = {a},
  pdfcontactaddress  = {a},
  pdfcontactcity     = {a},
  pdfcontactcountry  = {a},
  pdfcontactemail    = {a},
  pdfcopyright       = {a},
  pdfmetalang        = {en},
}

makeatletter
% Dirty hack of hyperref to make rgb-like links annotated with C mark become annotated with K mark to work in PDF/A with CMYK
% makeatletter - makeatother needed
usepackage{etoolbox}
patchcmd{hyper@linkfile}{/C[}{/K[}{}{}
patchcmd{hyper@linkurl}{/C[}{/K[}{}{}
patchcmd{find@pdflink}{/C[}{/K[}{}{}
patchcmd{hyper@linkstart}{/C[}{/K[}{}{}
makeatother

usepackage{amsmath}
usepackage{amsthm}
usepackage{amsrefs}
usepackage{lipsum}
theoremstyle{plain}
newtheorem{theorem}{Theorem}
begin{document}
tableofcontents
section {A}
{color{blue}Hello} World!
begin{theorem}
label{thm.1}
begin{equation}
1=1label{eq.1}
end{equation}
end{theorem}
begin{proof}
By reflexivity of (=).
end{proof}
Theorem ref{thm.1} is about the equation eqref{eq.1}.
See also cite{MR1727844}.
begin{bibdiv}
begin{biblist}
bib{MR1727844}{book}{
   author={Bourbaki, Nicolas},
   title={Algebra I. Chapters 1--3},
   series={Elements of Mathematics (Berlin)},
   note={Translated from the French;
   Reprint of the 1989 English translation [ MR0979982 (90d:00002)]},
   publisher={Springer-Verlag, Berlin},
   date={1998},
   pages={xxiv+709},
}
end{biblist}
end{bibdiv}
end{document}